Bad credit record for no reason

I paid my bill in advance thinking that in saving my self the hustle but I was taken to the lawyers. I then try to find out the reason I was put on hold for an hour ****il I hang up), no one I spoke to has a way of helping me, the lawyers say I should contact mtn, I went to the shop and no one had a clue n just gave me a number where no one answers mean while my credit score is affected. I need my name cleared cause my bill was paid last year for this coming year, my phones to be unlocked and my airtime and data back dated to the day my phone was blocked.