If you have a SIM in the phone than the only thing what prevents you from dialing anything is the cellular operator itself. If you don't have a SIM than it's m

If you have a SIM in the phone than the only thing what prevents you from dialing anything is the cellular operator itself. If you don't have a SIM than it's more complicated because the phone needs to register somehow in the network and, probably, indicate what it's trying to call an emergency number (so the network would allow both the registration and the call to occur). But my $10 on the dialer app just decline it.