I understand the situation for calls from the same company and one number. But for incoming calls with a mobile phone, the same person can call back dozens of times from a single number. In this case, all support personnel receive individual callbacks and the call center is locked for a single customer. Any callbacks from the same company will not know the extension number, so they will all fall to the company's operator and it will not be clear who called. I think if there is a callback, if the same number redials, the callback should be canceled or it should be able to play the "already have a call back then try again" sound with voice guidance.