Final answer:
XYZ Mortgage Company should not make unsolicited calls to Bob since he is on the National Do Not Call Registry, unless they have an existing business relationship or his express written consent.
Step-by-step explanation:
To comply with telemarketing regulations, XYZ Mortgage Company should not make any unsolicited calls to Bob since his name is on the National Do Not Call Registry. However, since his name is not on XYZ's internal do not call list, they may contact him if they have an existing business relationship with Bob or if he has given them express written consent to call him. XYZ should maintain records of this consent.