not upholding promise to give us a credit to account each month for 24 months for store employees mistake

In june 2025 we purchased 2 new phones, employee suggested for better price we switch plans. When all was said and done sounded great, we left. Got first bill, not even close to amount promised. Come to find out, girl in store gave us a promotion that actually didn't exsist. So after hours on the phone with various people and months later, it was agreed to give us a $54.00 credit monthly for 24 months,until phones are paid off. However the catch was each month we have to call to get discount applied. for 14 months i have names(they give fake names) and dates and info of call and now month 14 they claim our account can't get anymore discounts and they wont discount our account. First off we as customers should never have to call each month to get amount applied, and it's the fault of store employee and now they claim our account can't recieve anymore discounts. we aren't at our 24 months yet. I've texted, emailed and called and all the people are rude,wont help, and claim there are no notations on our account. What happened to all the notes. We are frustrated and ready to pay off phones and go somewhere else, but we shouldn't have to do that. It's cruel how they treat their customers. Even going in person nothing, each person on phone is in another country and their "back door" people claim they are the managers but wont help either. What do we do? horrible company