It does not have a limit as to how many messages you can send. we do not recommend sending more than 5000 messages a day. But when you send bulk messages users Maybe mark your messages as spam which will lead to your number being blocked. So take care to send messages only to your clients only. And the messages should not be spam or annoying advertisements. The messages should be services (reminders - OTP - subscription - or any message the customer is waiting for ...etc