Now suppose your electric company owned all the local Burger King franchises too, and decided one morning that Wendy's and McDonald's needed to pay 3x the current rate per kilowatt hour?
Would your response be, "Hey, Wendy's is free to go build their own hydro stationa and nuc plants if they choose?"
AT&T provides DSL and/or cable broadband in various markets, but they have competition from other cable providers and private DSL providers. There is no monopoly. As a matter of fact, broadband Internet is an extremely competetive market. This part of your argument is incorrect, so the rest of it falls apart and need not be addressed.