Upset customer

I am extremely upset....I've been with Xfinity for 3 years on internet but mobile only a year or two. This is my issue , if you check my account it shows a sage green Motorola razor and the device payments are 24.99. so when I contact support about my problem that's all that it shows so they tell me it's correct and I don't get anywhere. If you go back to the chat when I set up the account/made the order you will see that I told the chat agent I was on a fixed income and told her what I could afford for a device payment and I was told that this phone (Motorola razr) had a promotional offer of 8.99 per month for device payment. I could afford that. But they have been charging me 24.99 since December. And like I said nobody in the chats are able to help. As a matter of fact the last agent really made me mad because the only thing they wanted to offer to help me was for me to change my number to lower my bill... I've had my number for 15 years and Xfinity wanted me to port my number over to begin with and now they are offering me a deal to change my number...i just don't get it... The help department for Xfinity is very lackluster and I'm about to switch to T-Mobile for all my services