BotNotify does not have a limit as to how many messages you can send. We do not recommend sending more than 5K messages a day. But when you send bulk messages receiver maybe mark your messages as spam which will lead to your number being blocked. And to avoid that case, you can enabling Unsubscribe option.
When enabling that option you can see message text with unsubscription link that will be sent following your main broadcast message. And you can edit that message to, based on your needs.