How can I renew my internet service?

Hi. I've used Xfinity internet service almost a year and it's time for renewal. I'm quite satisfied with my plan so just want to extend it. I've tried to do it on the Xfinity website but can't find how to to it. What should I do? And I heard that Xfinity typically raise its monthly charge when they renew their service. Is that true? My budget is quite tight nowadays so I'd like Xfinity maintains its charge at least.