Refunds not paid to me since 2017

I settled my account with RCS last year 2017 and they were supposed to refund me and up to this day they have not. I keep receiving emails asking for proof of payment of which i have emailed and faxed through a zilion times . clearly their finance dpt is not doing their job. i have records of this in my emails. they are not doing justice at all. i will never ever do business with them again. i want my refund asap no matter how small the money is, i want it.