Disgrace on how they conveniently disappeared

We have double paid our cellphone account as my husband took over my sins account and he paid Nashua and I paid MTN. I I spoke to Nashua Mobile and in December a lady Palesa in accounts said she would organise me a refund and she emailed me a statement showing R988.63 uallocated which meant it was owing to me. She took my banking details and said a credit would be done. I have not received this refund. MTN have taken over MTN Nashua Customers and MTN tell me there is nothing they can do. Surely there is someone from Nashua still dealing with these issues. I am and have been with Nashua and MTN for over 10 years and this is how I am treated. I want my money back. I believe it is up to MTN to sort this out