Poor service

I bought a headset a week ago today. when I opened the package I realised that I had purchased the wrong headset and it was a PC headset instead of the ps4 version. I took it back 20 minutes after purchasing it and wasn't allowed to swap it for the ps4 version because I had opened the product already. They said they will take it up with head office and I should be able to get the ps4 version in a couple of days but they might charge me a handling fee. I've gone back 5 days straight now and head office still hasn't even responded to the store. Officially the worst head office I have ever heard of in my life. I've waited a week for them to tell me if they're going to charge me a handling fee for a product I opened and returned in the space of 20 minutes. I'm honestly appalled by the service of the bt games head office