billing, refund

I have been trying to resolve an issue with xfinity for about a year now.  I had xfinity internet and everything was fine until I added xfinity mobile.  I was automatically charged for the first month, but they said I wouldn't receive a sim card for a couple weeks and could start using xfinity mobile once I got it, which I was fine with.  I never received a sim card.   I called customer service many times, no help.  after 3 months, I went to my local xfinity store multiple times.  They called customer support for me each time, explained to them my problem, and eventually customer service agreed to stop charging me for mobile that I'd never been able to activate, at this point for 6 months.  I was charged for 6 months of xfinity mobile and was never able to use it.  They stopped charging me and agreed to issue a refund.  I NEVER received a refund.  Now, I have inconsistent charges on my bill, sometimes $63.00, other times $55.00, other times $103.00.  I cannot get ANYWHERE through chat, it just runs in circles.  I can't get ANYONE on the phone.  The store manager says they cannot help from here and this must be resolved through customer support. 

I have good internet service and hate to cancel, but at this point if I can't get this resolved, I'm going to ANY other service just for simplicity's sake.  This is incredibly frustrating.