Inconsiderate MTN

I had a contract with MTN which I cancelled and paid off the debt including the month instalment yet they still deducted and now I’m struggling to get my money back yet they said my query has been resolved with no further communication and when I reach out no one wants to assist it’s been over 2 weeks now of going back and forth with MTN and I keep reaching out but there is no proper feedback or what’s happening with my money and this an inconvenience and a bad way to treat customer