New way you handle phone service will cost a customer

I have been with Xfinity for over ten years and got the mobile services when it first came out because I worked for Comcast 8+years. I had a couple hardships last year that caused my bill to be late a few times but they were eventually paid.  Now I wanna upgrade my phone and do a trade in but not allowed to because I don’t have credit to purchase. If this will not be resolved I will be switching couriers