Misinformation from agents

I recently wanted to take advantage of the get a new phone on us promo.  I was due upgrade.  I called and spoke with agent and was told I would have to change my phone number to take advantage of promo.  I received the phone which was  iphone 17 pro, took it to xfinity store for help with activation and was told a new line was added to my account and this new phone was tied to my account. Was told by agent in store new line was added so original agent could get a commission.  I only have 2 people in my house.  Never needed a new line.  The new iphone pro was same size as the iphone 15 I was trading in so I asked if I could get the iphone 17 pro max instead as it was bigger phone.  I was told yes I could, I would just have to pay the $100 difference.  The store manager Charles told me he would put in a ticket for return labels for both phones and to check my email for these labels.  He offered to store both phones in the store safe.  I left both phones with him at the store.  I had to stop by the store repeatedly to check on the progress because I wasn’t receiving the labels in email.  This went on for two months.  I kept telling Charles I was being charged for this phone and he kept assuring me that any charges would be reimbursed once I returned the phones.  I stopped by the store last night and was told that they will not accept the return of my iphone 15, in fact they gave it back to me and advised me to sell it privately and now I have an unusable iphone 15 and a new iphone 17 pro max that I have to pay $1199 for.  How did this happen?  Why is xfinity’s solution to this misinformation by three different xfinity employees to blame the customer and make them pay.  I am an over 30 year diamond customer and this is how I am treated.  I will be looking to sever all ties with xfinity and comcast as they do not value long time customers and don’t stand by their promises.