Promotion cancelled

Early November I talk to an agent regarding my Tv, Internet and Landline package. The agent offered a good deal on the TV and Internet plus offered to transfer the phone line to Xfinity mobile with a free phone and $15 per month line charge. I received my phone the next day and during the activation process you get the option to change the phone number. I selected to change the number and activated the phone. This apparently canceled the promotion and I am billing for the phone and $45 for the line. There was no indication that selecting a different phone number would cancel the promotion. Talking to an agent he told this was my fault and there is nothing that can done about it. The agent was very rude and unprofessional. Having been a longtime customer with Xfinity I was planning on transferring all phone lines to Xfinity but with this experience I will start looking moving away entirely from Xfinity.