Angry client MTN failed to cancel contract and refuse to pay me back

I canceled my router MTN contract in 2024 and i gave MTN the reference cancelation number that I received from MTN but MTN continued debting my account. in 2025 I reached out again, asking why MTN is still debting me although I canceled and I'm never used the service since canceled. In 2026 I escalated the matter with MTN. I've been get different responses from MTN when I ask MTN to pay me back the amount of the money MTN has been debting from my account.All I want is for MTN to pay back all the money MTN has taken from me even though I canceled the contract. MTN representative told me that I should have checked my account and called MTN to inform MTN that debting order is continuing to which I disagree because as a client I canceled and have a reference number for cancelation.