Deals for Existing Customers - Misinformation

Hello. I've been a customer for years, and time and time again when I try to get a discount when speaking with a representative it fails. In fact, I was told a point that I would pay $xx monthly, but I must've signed the wrong document that they sent over because it ultimately charged me more, costing $yy monthly. I couldn't do anything about it even after contacting Xfinity support again because they told me that the $yy monthly price was all they could do, even though I have proof that they told me that I would only pay $xx . They send over a document for me to click a checkbox, but I must have missed the fact that they did not tell the truth. 

Anyways, I feel like I was deceived. I see this new customer deals and it's just so wrong that after being a loyal customer for years, despite the deception I wrote above, they still won't even lower it to what it was before, even if it's not in line with a new customer deal.