Yet another victim of the $830 for new phone [Edited]

I went in to an Xfinity store today to change service from T-Mobile.  While there, I was advised that my rewards account showed I was eligible for the $830 off a new phone for switching over to Xfinity.  All I had to do was to log in to my Xfinity email (which I never used before) and sign up to get the code.  Unfortunately since I never used that email account, I didn't have the password and could only reset it from my home wifi.  After an hour and a half trying to get ahold of somebody on the phone for Xfinity password reset so I could take advantage of the deal, I gave up and had to leave the store to reset my password at home.  The employee (who I will say was quite kind and had good customer service) showed me that I had that credit due to me for being a "Platinum" customer for being with Xfinity so long. 

I went home and reset my password so I could get the rewards program activated so I could take advantage of this deal.  I went back to the same Xfinity store and when they looked it up, the reward was magically all of a sudden no longer there.  It didn't even show that it was used and appeared as if it was never even in existence.  I called customer service and was told to call somebody else in the Rewards department the following day.  After spending a couple hours on this, and reading others' reviews about the run around they received from Xfinity, it is quite apparent that I'm another victim of this $830 reward scam.  I would like to resolve this, but because of this terrible experience I'm considering going back to T-Mobile.  I may pay some more, but I haven't been scammed by them.