Galaxy s3 "Not registered on network" error.
Just got a new boxed galaxy s3 from eBay (an unwanted upgrade) for £100 pounds less. It turns out that the phone was locked to T - mobile because it asks for a pin even though the network it available. Any attempt to call or send an SMS results in the above error. To check if your phone is locked type in *#7465625# as if you were making a call. If network lock says on then your phone is locked. You will need to buy an unlock code from the internet and the phone will be unlocked within 3 hours. If your phone is unlocked and you still get this error just activate your data on the phone.