Billing Enquiry

Good day <br> <br> Kindly assist . I seem to be having a billing issue with MTN , in September I had my cell phone service locked when MTN demanded that I make a payment of R625.43 to have my cell phone services reinstated , I made the payment on the 28th September for R625.43. A month later I receive another sms demanding a payment of R559, this is after MTN tried debiting R899 from account despite the fact that R625.43 was paid to them already. I made a call on the 17th October in order to cancel my contract since it was expiring and during that call I also enquired about the amount I am supposedly owing MTN , the agent checked for me and advised that they have indeed received my payment for R625.43 and there was nothing I was owing . I have just received another sms threatening to have my services suspended if I do not pay R559.38, Can someone explain to me what this is for ? what am I being charged for the remaining single line I have with MTN per month ? Please also confirm if my existing contract has been cancelled as per my request on the 17th October , the reference number I was provided with is ***, this is the same day I enquired about my billing problem.