Once we understand that personal information is going to be handled, the prudent thing to do is to limit access to the WhatsApp account. The first thing is to give operators access only from a platform like Callbell, only from company computers, never from mobile phones.
You can also add an extra layer of security by setting up two-factor authentication for the API you use. This will serve to generate a code in an Authy app every time you log in to the platform. They will also give you a list of security codes: keep it, it will be useful in case you lose your device.
As a user, remember that WhatsApp will never ask you for any code to execute any operation. On computers and platforms you log in with the QR code, not the one sent via SMS.