Xfinity promotion - stole my phones

I called a month ago to see what can be done to reduce my bill, the agent recommended removing the premium lines from my three lines to save $30. On my next bill my bill jumped by $108. When I called they told me I lost the credit I received from my trade-in almost $2500 value. I spend hours and hours speaking to customers service, back office, supervisors all promising to fix it and no luck, they escalated to main office and the person from that office offered $500 credit and I said I really want to get the full credit. She promised to talk to her boss and she said she will make it right and will get back to me then she won’t answer emails or calls. I called again and after additional hours of waiting and promises for someone to call me back nothing. agents are rude, on hold for hours. And not very professional, very disappointed with Xfinity,