Cellphone contract with MTN

Good day.....

Could you kindly please assist me regarding my MTN account that was handed over to MBD attorneys.till this date it is still pending yet I paid my outstanding balance in full.Earlier this year I started to receive calls from Nimble attorneys telling me that I owe MTN R3,133.to my surprise I thought the MTN account was paidup. so I explained to the consultant that I did pay the MTN account with MBD attorneys which still didn't help in anyway,because she said MBD was supposed to close the account on their side since it was fully paidup.i then asked for a paidup letter from MBD so that I can send it to Nimble.which fair enough I did.But still after sending the letter to Nimble they had issues around the way the letter was drafted and told me that they can't use the letter on my behalf.i am currently stuck with this matter that is even destroying my credit record because it shows MTN account. which I fail to get assisted with,even when I call MTN they failed to help me. Your assistance regarding this matter will be highly appreciated.

Regards Anna ***