I am paying for a service that i cannot use

I had a 24 Months contract with MTN, which expired 2024 March, i went to MTN Stores to cancel the contract and opened a Month to Month contract that I am paying on a monthly basis, now the service that I pay every month is suspended .I was told that my contract is not paid from May. I explained to them that that contract expired and cancelled when I was opening a new month to month contract, I am frustrated and not getting service on the contract that I am paying for. I have been calling and i was sent to legal and still I do not get assistance.