Finally recieved my $600 gift card from Xfinity Mobile. Activated with no issues. I was wondering though: has anyone had trouble using it? It seems to only work for select purchases. Tried to get gas with it, pay something online and neither would work. Tried a couple other purchaseas as well and nothing. I've used gift cards in the past and they worked for everything gas, online purchases, bill pay, etc. These, not so much.