Lying sales reps

I purchased a phone from Xfinity to replace my old phone. I was looking for the best deal as times are tough right now. To my surprise the sales rep told me I could get a new iPhone 17 for a small fee with no monthly bill because I was due for an upgrade. Here we are a month later and a monthly fee shows up on my bill. We called customer service and were told we are being charged $1200 for the phone. We got nowhere with customer service so I filed a BBB complaint and someone from Xfinity reached out to me. I explained that the sales rep had very clearly stated several times that there would be no monthly fee for the new phone. The representative from Xfinity told me it doesn’t matter what the sales rep told me. She said I would either have to pay the monthly fee or send the phone back to have it graded so I could possibly get a refund. This is absolutely ridiculous that I should have to be put out due to a mistake made by the company. I can’t imagine that it’s legal to lie to customers to get them to sign a contract just to flip the script after the fact.