Fix my billing

I had called MTN to cancel one of my contract 2 months ago, however this money i receive an sms of an amount due which includes the one that was supposed to be canceled on top of it all im told if i dont pay it my phone will be suspended in 2 days i just called the call centre im being given the runaround and someone just cut me off after spending an hour on the phone.... i dont mind paying but i will not be paying for a contract that was supposed to be cancelled end of May