Doesn't USA have any DoNotCall rules with some teeth, if, as the owner is saying, he "... asked you twice to remove me from you call list, as I have EVERY time I have been called by a representative from Groupon"? In my place, this would mean that their customer acquisition costs would skyrocket from fines for such incidents.
Clearly they don't care.
If "don't care" is a reasonable option, then that particular DoNotCall regulation is defective by design.