BT games has no after sales service

Be very careful when buying anything from BT games as they have a 10 day no returns policy which says a lot about there after sales service. I recently bought a battery pack from them for the new xbox series x controller and as it was fully charged when i got it i only ended up attempting to charge it about 2 weeks aftet i got it. when the battery died i tried to charge and it refused to charge. i then took it back to BT games who advised its no longer their responsibility to sort out and i must contact Microsoft directly. all the details BT games gave me to contact Microsoft are out dates and for over a week now i have not been able to contact anyone to get this resolved. i also attemped to register the product on the Microsoft store and the serial number doesn't exist so i don't even know if this is an actual Microsoft product as the package states.