Pathetic Customer Service

I immigrated to Portugal in September 2017. I paid my contract in full to cancel it as I was leaving the country. I even called retention services to make my number a prepaid one once the contract was over. To my surprise I started receiving debit orders again in October 2018, the renewal month of a new contract. Why was this happening? In December 2018 I went to a Cell C store in Wonderboom and no one was able to help me to tell me why I was being charged for this contract as I had paid it and asked to cancel it a year back. I finally got hold hold of someone at the service centre contact centre and they said that whoever helped me instead of terminating my contract rather chose to select that I was paying upfront for my contract. I explained clearly in 2017 I was to cancel the contract on renewal date and I was leaving the country . Really *********** service and I had to fly back to South Africa to sort this out and no one could still help me. I have now closed my bank account in South Africa and am receiving debt messages from NuDebt for mistakes from Cell C unacceptable.