My iphone carrier network doesn't work

Where the service bars are supposed to be it just says no service, and when i go to the carrier option i have to select it manually and then when i do, this message pops up - Restricted Network - your selected cellular network is restricted. You can choose a different network in settings. What does this mean! What do i do?

Probably, their carrier has blocked your service.may be its a network problem or payment of bills. Consult them. You can call them from other phone.