MTN South Africa have left me down

Hi

I have emigrated to Ireland from South Africa. I was an MTN customer for 26 years. Before I left I made sure that I paid the balance of my contract up so I didn’t owe anything. MTN then still decided to debit my bank account 1 more time afterwards. I contacted online support and they gave me a reference number *** which they said I have a credit. I have been trying to get the credit for 3 months now but no one ever comes back to me on email. I don’t have the South African number as cancelled it. Why if I owed the money MTN would be on my back but because they owe me the money it doesn’t matter to them. I am very disappointed as I was such a loyal customer and I never missed a payment once in all the years.