$200.00 Reward Card--Never Received= Bad Customer Service All Around

Signed up for Direct Tv and Internet back in December. They were offering 250.00 Gift Card for ordering online and then 200.00 gift card for Direct TV Signups. Thought it was to good to be true. I even asked the agent I spoke with if I would be getting 450.00 in Gift Cards, and her answer was yes. YOu are new customer and we value new customers.  I was impressed and thought that everything was going to be smooth sailing from here.  About 30 days in I received my first two cards @200.00 and 50.00 dollars.  Didnt hear anything after that about that last 200.00 gift card I chatted with an agent and she said to check back in 30 days and that was in March 2017.  Had alot going on from April till now and was going through files and found my notes to call back about gift cards. So on August 16  I did that and was told that too much time had expired and I didnt claim the last of the rewards.  I asked how could I claim something when I had never been sent anything like before and she just kept telling me that there was nothing that she could do for me.  This is honestly why i was so hesitant about signing up, because no ones word is ever kept.  I signed up for the rewards and because it was a great deal, and now I am regretting thinking that ATT would keep there word and send it to me.  Customer service agent was no help and today I called again and spoke to a agent, manager, and supervisor and all were rather rude saying I should have followed through and claimed my rewards when I received them.  HOW CAN I WHEN I NEVER RECEIVED THEM.  I have proof of what I was suppose to get and no one wants to see that.  So in December its bye bye to the company that cant keep there word and hello to another company.  I just want something to be done....keep your word ATT