Line closed even though I don't owe MTN.

I had a 24 months prepaid cell phone contract with mtn. I was billed 499 a month. I took out the contract in 2013 and in 2014 I paid the balance on the contract via eft after I got the balance from a franchise store which called mtn head office .fast forward to 2015 Mover I receive sms's saying I owe R61.40 and my line will be suspended if I don't pay it. I contacted the call center and I was told the amount is for increases that were effected and I asked why should I be billed as I already paid off the early cancellation fees? I was informed that unfortunately that's how it is. I still refused to pay it and wrote an email to customer care to which they promised to look into the matter and resolve it but they never did and my line was suspended in November to date. I involved lawyers and an email from mtn legal asrking for assistance to eactivate my account was sent and I even received an sms stating that my line will be reactivated within 24 hours but to date it has mot been activated. I don't mind paying the 61.40 but it's a question of principle for me hence I did not pay it. I can not be owing a balance on something that has been paid off. The number in question is ***