Free line with internet HELP!

I have the Xfinity Fast Internet plan (600mbps) and have received emails/mailers saying my Internet plan comes with a free one year mobile line. We signed up on August 16 and were billed in September for $42.81. I called and was told my Internet plan doesn’t qualify and the line will not be free for a year. Ironically, during the time I was on the phone with Xfinity, I received another email for this promotion. The Fast plan appears to have speeds higher than the 300k mbps plan required for this promo. We received our September bill for $42 once again. I’ve spoken to numerous customer service reps who say it has been resolved but it is not. Please help. Thank you.