dishonesty regarding promotion

I went into Xfinity Mobile to add an additional phone for my son and a new line for my daughter.  While there, the sales representative told me that there was a promotion that I could get a new phone for free when setting up new line.  I personally did not need a new phone or new line, but figured I would just do it to have a free second phone.  I was told that that all I would need to do was pay the taxes and that the monthly payment would be waived.  After the first month I received a bill with payment for the phone.  I called customer service and they said there was any issue with the new line.  After a long period of time they told me that I would need to visit the original store I purchased to resolve the issue.  I asked about sending back the phone as I didn't really need it, but was told that it was too late.  I visited the store and the costumer represented told me that I should set up a google phone number and then transfer the number and that I would still get the promotion.  So, I set up a number  and then called customer service again. They walked me through the process of getting the new google line transfer to my phone.  I was told that it would take a few days for the number to work, but that after this time I would get the promotion on my bill.  I waited and after the next month I once again got a charge for the monthly phone bill.  I called customer service again.  They told me that there was still an issue and that I would need to pay the phone fee.  It was too late to return and they would not give me the promotion credit that was promised both at the initial purchase and at subsequent calls.  I strongly believe that the original sales representative was dishonest with the original sale and that customer service was not knowledgeable and frankly incompetent in telling me how to resolve issue.  I have spent money and many hours dealing with a phone I actually didn't need.