Xfinity Mobile is overcharging me my about $120 per month, without resolution.

I have been frequently chatting with different chat support people over the past 2-3 months for a serious number of issues, and most never seem to get resolved.  I have had Xfinity Internet for 8 years with zero issues like this, but as soon as I sign up for the Xfinity Mobile it is a shit show..  I sent in 2 old iPhones which were supposed to credit me $1000 each to pay for my new phones.  However they are still charging me a device fee each month for my new phones.  I have been arguing with people over chat continuously and have been told things like well this takes 2 months, so just give it time..  Well it has now been 2 months, so today I initiate another chat, and today I am told I did not return the old devices quickly enough, so the promotion will be forfeited.  However they still have my old phones.  So if Xfinity will not honor the prices they quoted me then I want to cancel my service, but I need my old phones back to do so.  Or take the easier route and just fix my billing to match what was promised..  Still yet here we are 2.5 months the later without resolution.