Employee failed to tell me a promotion expired now I am stuck paying thousands of dollars for phones.

Back in September of 2023, TMO had a promotion called GO5G. I called them on September 19th to proceed with the upgrade so I could get the $830 off the iPhone 15. The phone agent (from India) never mentioned anything to me that the promotion expired on the 14th and allowed me to proceed with the upgrade. I spent two hours on the phone upgrading all 5 lines on my account and paid $30 for each line plus the taxes on the phones. After checking my account, I saw that it showed the old plan, and that's when I started reaching out to them, no one cared to call me to let me know (not a surprise there) and now, because of an employee mistake, I am stuck paying full price on all the phones when I traded perfectly good phones that were paid in full, mind you on their website, the promo was still showing so all they did after months of reaching out (chat and phone, agents saying they will see it through but never called me back), all they could do is offer me a one time credit of $109, and nothing else can be done. I have been with Tmobile for 21 years and 5 months. DO BETTER FOR YOUR LOYAL CUSTOMERS!

I really hope no one else has dealt with this, but please let me know if you have and how you resolved it.