The company buys a new number, imports a list of a thousand contacts, and blasts messages in the first week. Within two days, the number is blocked, and the conclusion is "WhatsApp blocks everyone." That's not quite right: a new number is fragile because it has no history — and history is built through specific behavior, not by buying a pre-heated SIM.
In this article
What "warming up" really means
Warming up is not about sending messages little by little until a button is unlocked. It’s about building, in the platform’s eyes, the behavioral profile of a company that engages in conversations — not one that just blasts messages.
The key signals are basically four: the ratio between messages received and sent, recipient response rate, absence of blocks and reports, and consistency over time. A number that receives as much as it sends, whose messages get replies and that is never reported, gains trust quickly. A number that only sends messages to recipients who never respond falls fast.
That’s why buying a "heated SIM" almost never works. What’s sold as heated is usually a number that exchanged automated messages with other numbers in the same scheme — behavior that doesn’t resemble real customer service and that the platform easily detects. You pay for a history that’s worthless and also take the risk of a number with an unknown past.
It’s worth remembering what actually causes a number to be blocked: it’s not volume alone, it’s reports, blocks, and silence. Warming up is essentially the process of ensuring these three don’t happen while you don’t yet have the reputation to absorb a misstep.
Why a new number is so fragile
A newly registered number has nothing going for it: no prior conversations, no accumulated responses, no lifespan. Any behavior outside the norm weighs disproportionately.
Add to that the typical scenario of someone who just contracted a tool: the urge to use the entire database on day one. It’s the classic combination — a number without history plus an old list without consent — and it almost always leads to the same outcome.
There’s also a detail many ignore: recipients of messages from a unknown number report much more frequently than those who receive messages from a saved contact. This means the first month should prioritize conversations with people who expect your contact — active customers, recent quote requests, or those who reached out via the website.
Finally, the cost of losing a new number is higher than it seems: besides the block itself, you lose the number advertised in ads, on the website, on business cards, and on Google, and you still have to notify everyone about the change. That’s why it’s worth spending three weeks doing it right.
Continue reading for free
Fill out once to unlock this and all other blog articles. We don’t charge anything — we just want to know who we’re writing for.
Takes 20 seconds. Prefer to talk directly on WhatsApp?
The 21-day plan
The volumes below are a conservative reference for a new number in commercial use. Adjust downward if you don’t have enough organic demand — forcing volume without real conversation is the opposite of warming up.
Days 1 to 3 — receiving only. Set up the complete profile (name, description, hours, catalog if any), share the number with existing customers, and respond to incoming messages. No active sending to anyone who hasn’t written first. Volume: whatever comes in, usually 5 to 15 conversations per day.
Days 4 to 7 — responses and follow-ups. Keep responding and start following up on active customers with pending topics. Up to 20 to 30 conversations per day, all with real context.
Days 8 to 14 — first active sends. Messages to those who requested contact, appointment confirmations, order notifications. Up to 50 to 80 per day, always to people who recognize the company. Here you should already see the response rate staying high.
Days 15 to 21 — controlled expansion. Up to 100 to 150 daily conversations, including first actions for customer bases with recorded consent. Monitor quality daily.
From day 22 onward, the number supports normal operation — and this is where the sending limit ladder comes in, following the official API logic.
Two rules apply throughout the period: never double the volume from one day to the next and maintain the ratio — if you send much more than you receive, slow down regardless of the calendar.
What never to do in the first month
Seven behaviors account for most new number blocks:
Import an old list and blast messages. People who don’t remember you report — and reports on a new number are fatal.
Buy a list. Besides legal issues, it’s the fastest path to mass blocking.
Send the same identical message to many people. Repetitive patterns are among the easiest signals to detect.
Send a link on first contact. Increases reports and reduces responses.
Use aggressive automation. Unofficial tools that simulate typing at impossible speeds give away the number.
Constantly change devices and tools. Session instability on a new number smells like irregular operation.
Switch to API in the middle of warming up. If you plan to use the official API, decide beforehand: switching restarts part of the process and has implications worth understanding in how the API works.
Warning signs during warming up
Warming up requires daily monitoring, not weekly. Four signs call for immediate pause:
Drop in response rate. If people stop responding, the problem is the list or the message — and continuing to send makes it worse.
Quality leaving green. In the official API, the number color is the most direct thermometer. Yellow on a new number is reason to stop active sends the same day.
Messages with only one tag for a long time. Sign of accumulated individual blocking.
Direct complaint. If someone writes "who are you?" or "I don’t want to receive this," treat it as a statistical signal: if it happened once, probably others thought the same without writing.
The response to any of these signs is the same: stop active sends, maintain only replies to incoming messages, and resume at half volume after two or three stable days.
Decisions that help before the first send
Some choices made on day zero make everything easier:
Complete profile from the start. Company name, photo, description, address, hours, and website. An empty profile increases the feeling of a scam and, with it, reports.
A number that makes sense. The area code of the region you serve conveys more trust for local business than a number from another state.
Promotion before sending. Put the number on the website, Google profile, and social media before starting. This way, part of the first conversations come from people who sought you out — the best kind of traffic for reputation.
Decide on QR or API beforehand. Changing paths midway is rework, and each model has its own rules for volume, cost, and templates.
One number, one purpose. Mixing customer service, collections, and promotional campaigns on the same new number accelerates reputation decline. If volume justifies it, separate them — and warm each with the same care.
When changing numbers is the right decision
Warming up a new number isn’t always the best solution. Before starting from scratch, check if what you have can still be recovered:
Number with yellow or red quality but active. Usually recovers in two to four weeks with volume reduction, list review, and focus on customer-initiated conversations. Changing here means throwing away existing reputation.
Number with temporary restriction. Also recoverable. Wait out the period, fix the cause, and return slowly.
Number permanently banned. Then there’s no choice — but before activating a new number, understand what caused the ban, because the same behavior will bring down the next one in days.
Owner’s personal number used as commercial. Planned change is worth it, with prior notice to customers and a coexistence period of both numbers for 30 to 60 days.
If the change is inevitable, notify beforehand: message the active base from the old number, update the website, Google profile, and ads the same day, and set an automatic reply on the old number informing the new one. Half the damage from changing numbers doesn’t come from the platform — it comes from customers who tried to reach you and thought the company closed.
Mistakes that force starting over
Buying a "heated SIM". Artificial history that doesn’t fool the platform and comes with an unknown past.
Rushing with the old database. The database will still be there in three weeks; the number won’t.
Scaling by calendar, not by signals. If response drops, it doesn’t matter if it’s day 15 of the plan.
Not setting up the profile. Takes ten minutes and reduces reports.
Ignoring opt-out requests. One unresolved case becomes a report, and reports on a new number weigh heavily.
Using the owner’s personal number as the "new company number". Mixes personal history with commercial use and creates the ownership problem discussed in when someone leaves the company.
Giving up on warming up because "it’s slow". Three weeks of discipline cost less than a month rebuilding presence with a new number.
Warming up is, at its core, proving through behavior that you are a company that converses. There’s no sellable shortcut for this — there’s a sequence of days where the number receives as much as it sends, no one reports it, and people respond. Done this way, the number lasts for years.
Frequently Asked Questions
How long does it take to warm up a new WhatsApp number?
About three weeks in real commercial use: three days receiving and responding only, four days following up on active customers, one week with the first active sends to those expecting your contact, and a final week of controlled expansion up to 100 to 150 conversations per day. The rule throughout is never to double volume from one day to the next and to maintain the ratio between messages received and sent.
Is it worth buying a heated SIM?
No. What’s sold as a heated SIM is usually a number that exchanged automated messages with other numbers in the same scheme — behavior that doesn’t resemble real service and is detected by the platform. You pay for a worthless history and take the risk of a number with an unknown past, which may already have accumulated reports.
What to do if the number’s quality drops during warming up?
Stop active sends the same day, maintain only replies to incoming messages, and return after two or three stable days at half the previous volume. Yellow on a new number is a serious sign because there’s no history to absorb the misstep. Also review the list and message before resuming: quality drops almost always come from sending to people who didn’t expect the contact.
Centralize customer service without changing your number
Connection via QR or official API, single queue with a defined responsible, customer history that stays with the company, and sales funnel on the same WhatsApp panel.