No. More like if you are on Comcast, you can't access Twitter. If you're on AT&T, you can't access Facebook. When you sign up for your ISP, you get to choose between Amazon and Netflix, and you can't change your mind without paying someone to come out and lay new line if you're even one of the tiny few lucky enough to have more than one ISP that serves your home.

If Facebook and Twitter were also ISPs and you could only intereact with them and not with any other social networks.