I could see the issue if it was a broader scope, but they turned off a service that they implemented as a courtesy to people who travel via the underground.
I could see the big issue if they turned off service in a whole city or a whole area, but turning off their network at their discretion to possibly avoid a riot is well within the rights to do so, as I said its no differant then me turning off my Public access points because I don’t like what people are doing. It’s not like your home ISP or your Cell service you pay for, they did not turn off Verizons/AT&T/Sprints towers, they turned off their repeaters (im assuming their simply cell repeaters)
I don’t think that it was something they needed to do or was necessary in any way but they did not realistically violate any rights.