Internet access should be regulated like it was a utility however, and that's the great failing of public policy in that area.
To give you an idea, a residential phone bill from 1982 with unlimited local calling in Seattle was around 13.50 inclusive, in 2019, that same service cost 50 dollars - inflation alone would expect the cost of that service to only be 36 dollars or so - and technological advantages should make that service cheaper, not more expensive.
AT&T was a different company, at one point before divestiture they were the single largest private employer (1973) in the US, providing union jobs with good benefits and stable (effectively) lifetime employment. Beyond this, they were also a leader in providing equal opportunity for minorities.
The money generated by AT&T was paid back in technology dividends - dividends that underpin much of the technological innovation we've seen over the last 60 years.
AT&T's disaster preparedness is a whole other topic that could be gone into as well.
My read of the parent comment is that monopoly era phone service from AT&T was cheaper when compared to phone service in other parts of the world during that era.
I can't speak to the veracity of this claim.
Nationalized companies are owned by the state. AT&T had/has private shareholders.
2) Control
With ownership comes control. The U.S. government granted AT&T a conditional monopoly. In the early 20th century it was in exchange for extending service across the nation. Mid-20th century for defense work.
Aside from these conditions the U.S. government did not exert control on AT&T's operations.
I feel like this is being pedantic. While there are shareholders, taxpayers have funded the infrastructure and are paying for it in the form of tax breaks.
No.
Until 1982 AT&T in the United States was a legal monopoly, not a nationalized telecom.
The book, The Idea Factory about Bell Labs has most of the history including why the the defense work Bell Labs did during WWII and beyond helped them justify a nationwide monopoly on telecom.