There are two ways a seller can request a Callback:
#1: A contact can click Contact in the user profile on their Home Value Dashboard.
#2. A contact can also click Seems Incorrect? Contact Me if their home details are not accurate.
In both cases, the contact can enter their name, phone number, and a brief message for the user. The reason for contacting may vary, so it is important to respond accordingly.
Check out this for article more information on how to view Callback Requests.