Samsung S6 Battery

I upgraded to the new Samsung S6 on friday 10 April only to have no battery the next day with no simcard in phone. We tested the phone over the next few days and was told that we had a 7 day return guarantee. I took the phone into Gateway within that period and they have taken the phone to be tested so I now sit without a phone losing business as I run my business from my phone, only to be told it will be expected back on friday 24 April. I really think this is shocking service in this day and age as clearly there is a problem with the S6 battery and not my fault on a brand new phone. They should have replaced it immediately.