We strongly recommend to connect official WhatsApp product, which is always stable.
Messaging in Bitrix24 via WhatsApp. Messaging should be performed by business messengers only, for example by official WhatsApp.
ChatApp smart messaging via WhatsApp. Messaging may be performed in any messenger, for example, WhatsApp WEB, since smart messaging sets pauses and does not send all messages at once.
If a client does not use WhatsApp, you may use integration with Telegram personal.
For messaging in WhatsApp use official product for business where the messaging is limited only by your budget for internet traffic, but remember, a client may add your number to a blacklist.
For connection of official WhatsApp you don’t need a phone, any active WhatsApp number could be connected to official integration. Recommended.