Free Xfinity Mobile line

2 months ago I upgraded my internet package (member for over 9 years) and was offered a free mobile line for a year several times.  This was promised with no charge.  Activated service on old iPhone for my daughter.  Now I am being charged monthly and showing a past due balance.  After receiving texts and alerts of collections and service shut off, I contacted Xfinity and have been told it was not a free line, then it was "absolutely a free line", to now I do not qualify for a free line since at some point I had a prior Xfinity mobile service.  I advised them that if it was not a free line I would be cancelling it and was not willing to pay a dime since it was promised and they should have caught any issues with the free promotion.  Now in order to cancel the line they want me to pay and trying to blame me.  I have had nothing but issues with Xfinity for the past several months, including internet connectivity issues (took weeks to resolve and all reps told me they were the expert to get the issue resolved).  I am at the point to cancel all services with Xfinity and move on.  Their customer service is terrible and they are unwilling to help.  All issues with the internet were met with "have you thought about a mobile line".