Why is my bill so high?

Switched to Xfinity Now prepaid internet a couple months ago, was on auto pay but now I'm getting a late notice and my bill is way too high. One, why is the bill so high, and two, why is it not automatically paid? How hard is it to do prepaid internet right?

Also, went to make a payment and apparently I "don't have xfinity services" and can't pay... (don't get me wrong, I'm fine with not paying, as long as my internet service continues. As it is I've overpaid too many times and had to deal with your horrible customer service WAY too many times already).