Mobile free for one year

I upgraded my home Wi-Fi with a cherry on top being when you’re a free mobile service. I called and ordered service along with an iPhone. When the iPhone arrived, my mom seeing how much it was and sent it back. I didn’t purchase an iPhone call to add that to the one year service and was told that I no longer can get it due to expired promotion code. The agent said I now have a history of mobile service when I never even spoke one word or reported my number over to Xfinity. I would like to say this is just my problem is really leaving a bad taste of my mouth. Especially with Xfinity being one of the leading companies in technology. I also can’t see how the agent, supervisor and or mobile service department cannot solve this minor problem. Can you please explain to me why I cannot get my one year service for mobile?