MTN Account Closure

MTN has handed over my account to debt collectors but the debt collectors say I am not owing MTN and therefore they cannot accept money from me and they revert me back to MTN.A guy from MTN called me to assist with closure of my account and he said he would speak to their internal legal department so they can advise on how I can make payment and close the account but it has been 3 weeks no one from MTN has gotten back to me I cannot pay at the MTN store as they say my account has been handed over .I want to pay and close my account but MTN has been making me go around in circles and this is affecting my credit score .