bad service ever received

I went to spec saver to collect my spectacles then when I get there I was told to pay extra fee as the medical aid was not going to cover alright I did that but when I check the invoice it actually belong to someone else, since they promise to refund me still today now they telling me they will not pay me back because the medical aid has not pay them and that was not the agreement from the first place, in other words they will be getting double amount with one client , don't always assume big companies they have values no its not like that, they don't treat customer's with respect at all.