15% Admin cost is a *******

I needed a wifi router. I went to Southgate Mall on Friday 23rd July 2021. I saw a router at game. I then decided to see what hifi corporation had to offer. They had the same router for a cheaper price. I purchased it for R559. I brought it home and connected it. It was cutting off the telephone line. I then contacted telkom as the service provider. The line with the new refused to sync. On Monday 26 July 2021 I went to the store and told the staff at consumer services my problem. Firstly, they were very unprofessional. Secondly, they looked at the router. Everything was original. The staff then went to the Manager and came back to me notifying me of a 15% admin charge. I wanted my money back. I agreed . Then the staff tells me we don't have money in the till. I told him I am not from the area and I can't come back. After about 20mins they finally refunded me. My complain is the 15 percent admin cost. The item had to be opened to be tested. The item was returned in its original packaging including the plastic coverings for the router. The thin plastic film that covers the box was the only item that was torn off. That's obvious because the router cannot be removed from the box without taking off this thin plastic film. In fact I returned it with this plastic film together with a plastic barcode that was stuck onto this film. I don't think I will ever walk into another hifi corporation store again. When I mentioned that to the staff, he retorted by saying it's fine you don't have to come back.