Callbell is a good option

“The overall experience with Callbell was good, even with some things to improve as a multi-user software, and it's a good alternative for getting started in the multichannel customer-service market. Among the main advantages are the option to add several WhatsApp numbers within the same platform, plus other services like Facebook Messenger. As a downside, the multi-user feature could be improved — for example, having two agents connected simultaneously on the same WhatsApp number.”