Sprint last week became the latest cell phone carrier to offer service on the Red and Purple lines between Union Station and 7th Street and Metro Center, but talk fast: that's a five-minute ride.

The Los Angeles County Metropolitican Transportation Authority has been negotiating with providers for months to offer service on the trains and it's been slow going.

T-Mobile is scheduled to begin service by October. But there are no start dates on the calendar for other providers like AT&T and Boost Mobile.

For several months now, lucky Verizon users like Kevin Perez have been texting, emailing, Instagramming and even Pokemon Go-ing on parts of the Red and Purple Line subways.

Asked on Tuesday how his cell works in the subway at the 7th and Metro stop, Perez said: "Really good. It's really fast."

Perez said the service saves him time because he can answer emails and phone calls when he goes out to lunch.

But riders like Boost Mobile user Bill Tucker are out of luck for now. Tucker said his lack of service makes him nervous.

"An earthquake could come and we’d be stuck down here," he said. "Anything could happen and you can’t call out."

Safety is a continuing concern with the lack of cell service on many Metro trains and buses. After a terrorist attack on the airport and train system in Brussels in April, Metro riders expressed worry about whether they could use their phones in emergencies.

Metro officials expect T-Mobile service to be up and running by October. They are still in negotiations with AT&T and other carriers with no start date scheduled.

Officials have said they hope to expand cell phone service to the full subway system by 2017.