Customer of 20yrs lied to how to get help

Let's start off with I have been a customer with att since 2005.  Actually before they even made the switch from cricket to att in 2005.  I have never been as unsatisfied with the service I have received until now.  About 2 months ago I needed to upgrade my phones.  One had not been upgraded for 6 yrs and the other line for 4 yrs.  So when I say needed to I needed to upgrade.  I call costumer service to see what my upgrade options are and I'm told that existing customers no longer qualify for any kind of promotion going on.  Ok so I'm upset I look in to switching carriers Verizon offers me about the same plan for the same price and promotional pricing on my phones as well as gift cards for switching. But silly me I have some strange loyalty to a company I have been with for almost 20 yrs call back to see if there is anything I can do to possibly save something on the new phones.  I am informed by the representative that all I have to do is add a new line and we can get that discounted promotion on all of our phones.  So I'm going to save $13 on 3 phones.  Of course I have to add a line or possibly a tablet.  I have a 14 yr old grandson he doesn't need a phone but I off him the tablet at which point he says he would rather have a phone.  Ok fine we drive the 45 mins to an authorized att retail store so maybe I can look at a phone before I purchase.  Everything goes fine no problem in the store.  I leave with 3 galaxy  s9 plus.  I know my bill will be higher I expect that but am shocked to see when the bill comes 2 months later. Of course after the 14 days I have to return the phone.  That the only discount I have is for the new line i added( that I didnt want or need anyway). I call costumer service once again am told that the promotion didnt cover upgrades.  I forgot when I started working at att and was supposed to no the fine print of all promotions.  Was told there is nothing she can do and to talk to the loyalty department because they should be able to help.  No they cant help nothing she can do because yet agian there is no proof that some one told me this.  Which is very convenient.  So I guess I just decided to add a line that I didnt want but for the upgrade to be part of the promotion I need direct TV.  Now every agent I talked to pushed this crap down my throat about direct tv but none of them said I had to have it for my promotion.  Apparently there nothing the company can do.  I have never felt so lied to and mistreated over $30.  I'm still paying more monthly then I'm saving.  I'm understanding in the fact that the phones are more expensive and att cant give them away for free.  But I was mislead and I dont think it was intentional but u agents dont even understand the promotion so how should your customers. My question now is who do I need to talk to to fix this problem do I need to write a letter talk to another department or what.  Because my loyalty has caused me nothing but problems.  I could be at Verizon right now with the 3 phones if I wanted paying half price for the phones as well as having an extra $300 I'm my pocket.  I dont want to pay off these phones and leave this company but as upset as I am that $3000 for the phones would be worth it to never deal with something like this again.