Promotional baiting

Spouse was deployed for 9 months. We shut off his line. 2 months prior to return i reached out and was told he needed a new line and was offered a promotional- free phone and line for a year if I upgraded internet. I agreed as seen by e signings- chat screen shots and the phone received in mail. 

I kept seeing the charge for his line so I reached out only to be assured it would drop off. Today I saw it was still there so I reached out again only to be told they now wont honor the Promotion despite 2 months of being offered- told and agreed upon. 

Allegedly now its because we are existing customers- if that was policy we shouldnt have had it offered and agreed upon. If its a mistake this is on them- if not its clearly a bait and switch tactic. I have now upgraded internet for now reason- they didnt honor their contract and I am now only being offered a 20 dollar ine time credit.  We have been loyal customers for years and are now considering leaving.