Dont overpay AMPATH

I requested banking details in April of this year - 2019. Paid Ampath. Month later they let me know it was too much money. Asked to complete transfer request to pay me back. Gave it. They then send me an email requesting my sister's 'consent' to pay me back. ***? Money was MINE from MY account etc etc. I wrote them a snotty email. Eventually sent the stupid consent. It's nearly August - I am STILL waiting for my payback. What a bunch of idiots!