Why is my phone showing 'no service'?

[iMore Question]

my phone is showing 'no service'

phone worked ok this morning for a imessage but now i cannot either make or receive calls, text, upload call time.
I have a pay as you go, and am with o2.
yesterday - i could not recevie or make calls and I reset a counter on my settings but the 'no service' message is new

 

[bamf-hacker]

Re: my phone is showing 'no service'

Try to reboot the device and if that does not work I would contact O2 to check your account.