Company officials said they were blindsided and mystified by the strike call.

“We’re baffled as to why union leadership would call one when we’re offering terms that would help our employees — some of whom average from $121,000 to $134,000 in total compensation — be even better off,” said AT&T spokesman Jim Kimberly.

» RELATED: The talks before the strike

Company officials were adamant about being prepared for a walk-out. In the days before the contract expired, AT&T officials said they would be prepared for a strike and that business operations would go on smoothly with managers, executives and contractors picking up the slack.

“We’re prepared for a strike and in the event of a work stoppage, we will continue working hard to serve our customers,” Kimberly said on Friday night

Union leaders scoffed at the notion, arguing that the company will have to prioritize work delaying new installations and non-emergency maintenance.

Reports on Saturday indicated union members were picketing at some AT&T sites, including in Georgia, Florida and Alabama.

The union said it has filed an unfair labor practice charge with the National Labor Relations Board, arguing that the company has not bargained in good faith.

The union’s Southeast region includes technicians, customer service representatives and others who “install, maintain and support” the company’s landline and internet line services. The region includes Alabama, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee.

» RELATED: Rallies ahead of the strike

Union officials have said that the key issues are job security and a steady rise in healthcare costs.

The timing of the strike gives the union leverage in some ways, but favors the huge company in others.

To the workers advantage is a tight labor market in which a low unemployment rate has many employers complaining of a shortage in skilled workers.

But changes in technology allow the company's day-to-day operations to continue smoothly, which may encourage AT&T to try waiting out the strike.

And the federal agency that the union is making its complaints to, the NLRB, has become more conservative over the years even as the influence of unions nationally has shrunk.

Moreover, the South has long been a region with fewer union members and governments that are typically not sympathetic.

That backdrop has made many Southern unions reluctant to strike. But some telecom workers have said they are under continued pressure, that wages are rising more slowly than costs while the company shifts to lower-paid jobs and contract workers.