ATT Fiber Reward Card

I was looking to switch from ATT Fiber to Google Fiber back in July, an ATT Agent called me and they offer me an upgrade to 1Gb with $100 reward card after 3 months of usage, now when I was trying to redeem my gift card they said it is expired since you don't redeem it within 120 days and you no longer have a reward card. WHAT!!! I did not got any mail or email for this

IT IS THE TIME TO SWITCH