Contract Terminated

I had a agreement with Nashua Mobile but I know they sent the contracts over to the service providers, which in my case is MTN. On the 2nd October 2015 I emailed them to say I am not going to upgrade on the 11th October, I am rather going to let the contract terminate. But I would still like to use the number but as top up. But I don't need any extra's like mega bytes ect. sent to my number. I will buy if need be. <br> To my surprise I go a unpleasant sms this morning, My service has been suspended as I have reached my limit of R500. BUT I ASKED FOR THIS TO BE TAKEN OFF AND I HAVE BEEN PUTTING AIRTIME ON MY PHONE ASWELL!<br> Then I get a sms saying my account has been credited with my monthly 200MB data WHICH I ALSO ASKED TO CANCEL!<br> This is the reason for people not having good credit records cause some people cant do their work! And MTN must please not come back to me saying that its my fault or something I haven't done properly cause their agreement said I must let them know in writing before the termination date that i have decided to not proceed with the contract. Which I did which they even responded on!