Lied to about promotion

I guess I'm not special. Though this is the first time in several years it's happened to me. They gave me the deal, then added a line without telling me. After a few months of autopay, I asked about it and they said it's a mistake, we apologize, and they give me a credit. They then tell me they will reinstate the discounted installments. This month, they said I canceled the line so I don't get the discount. Nothing in the notes and we can't do that unless you want the line you're not using back. So now we've got an overpriced phone and a company that does not stand behind its own words. Don't tell me it's not in your notes.