MBD debt harrassment.

I have been harrassed by phone calls from this company. I am currently not working and I have made a payment arrangement and I still receive countless phonecalls After I make a payment they claim I have not paid. They call from as early as 07:00am every day leaving countless SMS's. I don't understand why I made the payment arrangement in the first place only to get told it's not enough and to be continuously harrassed.