Mobile plan is NOT what I was offered

I am absolutely sick of Xfinity!! After numerous phone calls and being told it will be investigated into nobody has fixed my problem. On April 25, 2025 I was offered $400 off a new cell phone and service for 1 year only paying taxes each mo. (under $5). Of course my first bill was much higher than expected.......didn't get the per mo. service correct OR the $400 off the phone plan. I am sooooo tired of the many phone calls and outrageous amount of time on them and still not getting this issue resolved. I am being told that they cannot see the offer I was told I would get in April so they have to research it. OMG! would anyone switch cell phone providers without a discount on the phone?? Seems like a given. I told them to go back and listen to my phone conversation and they would see that I was indeed offered all this. So on Oct. 11th I finally had a conversation with a person who said she would have the department on the line at the same time who could fix this and get this resolved. At that time they gave me a $100 credit and said the next day there would be another $100 credit and they would investigate into this before I would get the remaining $200. Well the second $100 did not happen so still waiting for the remaining $300 credit. This is INSANE!! I do have a ticket number and called another time about 2 weeks ago and was told to give it more time. Besides Xfinity mobile I have been a television and internet subscriber for almost 40 years. How can they treat their long time customers like this. Paying $258 a month for that. So my decision is to dump both if this isn't resolved very soon. It has been over 6 months.