Wrong amount payment

My partner and I have fibre with Metrofibre, it’s on my partner’s name but I make the payment every month from my bank account. Last month I made a mistake and paid R5900 instead of R448, I called Metrofibre to let them know of the mistake I have made. I spoke to a lady called Thuli and she told me to send through my proof of account and the proof of payment of the bank account holder that the payment was made from. I did that and Thuli told me I would get my refund in 7 days. It’s been a month and I decided to call them and find out when I’ll be receiving my refund, now they telling me they can’t refund me as the fibre account holder is not the same as the bank account holder. But when I spoke to Thuli the first time she never told me any of that, these people are ****** and I have sent them the proof that the bank account is on my name.