Hello,
A $4.00 increase sounds like a Franchise Fee or tax situation. Maybe a programing surcharge? I would go to Twitter's Ask Spectrum Page. Get an account and follow them. (Or log in to Twitter.) Send a Direct Message (Private Message) to them, by providing your account information.
Here is the page:
https://twitter.com/ask_spectrum?lang=en
Our community is great for just about any other peer-to-peer support questions about Spectrum products or services. But the Twitter Guys at Spectrum would probably be better for assisting with billing questions. Ask Spectrum on Twitter should be able to say exactly why there was a billing increase.
Satch