Total-sports account handed over MBD

i received calls from MBD telling me that my total-sports account was handed over to them. they told me i should make payment arrangement with them. so they said i qualify for 40% discount if i settle the outstanding amount in 1 month, or 30% in two months. i requested them to sent me contract in writing that states everything they are saying and summary of my debt. they hanged up phone for me. they keeps on calling me and harassing by ( repeated calls, calling me when ever they want, abusive or obscene language), making treats like ( coming to my work place) they try to manipulate me in paying off my debt telepathically but when i ask documents to be sent to me is a problem. when i try to call them they do not answer.

please help me.