Question:

Why do the Call Date and Call Datetime fields get updated when a signature is captured on an Offline Call?

Answer:

When using Offline signature capture, the default functionality of Veeva CRM is to overwrite the  Call_Time_vod__c and Call_Datetime_vod__c fields with the value of the Signature_Date_vod__c once a signature is captured and accepted.

To maintain separate call and signature datetimes, enter a value of 0 in the Disable Call Datetime Overwrite Veeva setting.

Related Documentation:

CRM Help Documentation: Maintaining Separate Call and Signature Datetimes