ONE last chance with Xfinity Mobile before cancelling

I am on my 3rd hour of chats and phone calls. Simply, you would think, I want to upgrade one or both lines with trade-ins and keep my current plan as I have done for the past 20 years as a Comcast/Xfinity customer. I have the two mobile lines and Xfinity Internet. Every time I open the Xfinity page I am presented with different options and different plans and pricing. NO one person has been able to answer all of my questions and guide me through this process. The last agent has told me I can only upgrade if I pay $90 per month for my two lines plus my phone payments which is $20+ more per month than my current plan. I then see a plan called $600 Plus Up which again I cannot get a clear explanation of and as it is written I would qualify for and not have to change my plan?

Why am I chasing Xfinity to remain a longtime and loyal customer?

Please, can anyone assist me?