Harassment and unprofessional from MBD

I receive calls at least twice a day and SMS every second day saying I have not responded. They are the debt collectors for Shapiro Attorneys who has been payed over a week ago. I tried to contact MBD's office to rectify this issue as I know the call center can't remove it from the system. The moment I try explaining the issue and saying I have paid they drop the phone. As lawyers do they think thst harassment charges can not be opened by a person who owes them nothing. This review will be taken up with Shapiro Attorneys as they are hiring MBD. Best to get professional debt collectors.