Not Treating the Customer Fairly

I paid for my pre-paid service on the 15th Dec, on the 23rd Melon Mobile made an unauthorised debit (paying twice for the same service in a month), I brought this to their attention the same day, I was requested to furnish Proof of Banking details, which I did (still the same day) and was informed that the refund will take 24-72 hours, today is the 30th yet this has not been done yet, I once again took it up with them and I was told that my refund was not authorised yet, they have escalated to management but no timelines were given only apologies. I do not understand why a refund should take this long, considering that I am not in the wrong and that Melon Mobile went beyond their mandate by debiting my account without authorisation, worst still is that I am only getting apologies, no specific timelines...Is this in line with TCF clearly not.