have robbed me blind! Bitcoin payment gone bad

Owning a few Bitcoin I finally decided to try and buy something with them. Hearing that accept Bitcoin as a valid payment method I was delighted all those lush goods buyable with my virtual coins. I filled my basket up with goodies that totalled up to 0.553875 BTC on checkout I chose to pay via Bitcoin... made the transfer and then got this error "payment via bitcoin failed as payment amount does not match sale amount" to be fair using blockchain I had factored in a transaction fee of 0.0002 BTC which I made a slight mistake on so I ended up over paying by 0.0001 Bitcoin.

After a few emails back and forward to Fancy support I have got this outcome 'Thanks for the additional information. Our site works best on Google Chrome or Firefox and we tend to see errors when another browser is used. Please make an attempt using one of those and let us know if the error continues.'

So i'm out of pocket 0.55 BTC and the response for this daylight robbery is to change my browser and try again. Utter madness.

Any feedback on the issue would be hugely valuable.