settlement letter

i have two contracts phones with mtn and was unable to pay for my account then legal department listed me to some company that i should make payment arrangement with but i cannot seem to get contacts of that company and when i called mtn they said that the amount has been paid off.

please assist me with proof or maybe a settlement letter so that i may settle the balance. i called the mtn and they said they provide me with proof but it been a week and days now with reference number ***2

please assist