it's upto their tracking policies. they can see which sites you visit, apps you use by dns queries. Use vpn to hide yourself from wifi providers as well as mobile service providers
Absolutely your ISP knows a lot more about your browsing than you think. Everything you browse goes through your ISP's server even your private info, however most if not all of the info that goes is encrypted. Your ISP can determine which site you visited, which page you visited, from where you surfed the Internet and not just that they can pretty much guess how many characters your password have by looking at the size of the dns request.
