Is it so difficult to allocate a payment

I had 2 contracts with MTN, cancelled the 1 because it was up. My payment reference was still the cancelled contract number, but this is linked to my existing contract. I made payment on 28.09.2017 and was receiving sms' about my overdue account. I spoke to Sydwell Nyembe on 02.10.2017 after receiving another sms about my overdue acc. I sent proof of payment and this payment was to be allocated. On 04.10.2017 I received another sms and sent him an email stating i'm still receiving the sms and never received a reply from him. I received the sms again yesterday and today my service was suspended. Can somebody COMPETENT please allocate the payment on my acc!!!!