Why am I getting billed for free mobile?

Activated new Xfinity Internet 2 months ago, and was offered (several times on multiple calls) a free mobile line for 1 year. Took the deal. Despite this, I've somehow incurred monthly mobile charges for the last two months. Xfinity autobots ran me in circles twice when I inquired.  Called customer service twice- was disconnected both times at the exact same point: after pressing 1 to speak to an agent. 

Whatever the explanation might be for the recurring charges, it: a) was never communicated to me, and b) obviously conflicts with "free", no matter what justification is offered. Good companies maintain consistency with customers and charge accordingly. The consistent outreach to correct one thing or another in the last 2 months is pushing this relationship towards "enemy" territory.

I'll need a prompt callback to explain the unexpected charges.