$800 credit not being applied

I traded in a phone that was on the list for an$800 credit. I took screen shots showing it was going to be $11 more a month. Talked with chat to verify it was correct before the purchase. They said yes. $22 credit will be applied every month for 3 years. My screen shot shows $27 for 2 years but they said $22 for 3. I told them I wanted to verify before I purchased. They said it's good to go but give it 2-3 billing cycles to level out. So made the purchase sent my almost new S9 plus back with original box. Today my account says I can only receive a $27 credit and that is not a month. Next future bill shows $33 a month more not $11. I went on chat they said they would give me $400. I said no I want what I paid for. They said I would have to upgrade my plan to a different 5g plan but would give me a $10 loyalty credit. Then I could get the $800 trade in. I explained that I had my receipt and screen shots of the purchase which says $11 a month. They said my receipt was calculated wrong. Now they want $23 more a month which is an extra $432 over the 3 years. How can this be resolved? I see people have had this prob for the past 3 years. Seems to be a bait and switch or false advertising especially when you have a pictures of the price and checked ahead of time to confirm. It seems you have to chat and hope you get an experienced person to resolve. I just spent 2hrs on chat and said my only option was to upgrade my 5g plan. Then the system was down and they want me to chat again. So frustrating. Thanks Frank

Re: $800 credit not being applied
Customer Service Rep

Hi there. If all promotional requirements are not met our system will auto remove the promotion. There is no way for us to stop that. If the promotion has a plan requirement to get the full $800 off you would need to Upgrade the plan. You do have 30 days from purchase to return the device. I am sorry if you were not aware this required the premium plan, but this is all outlined in every promotions details. Does this make sense?