I have a Nokia 2600 here that shows the SIM Not Valid message with O2, Orange and Vodafone SIMs.

I don't know what network this phone is locked to.

I want to unlock the phone, but of course the DCT4 unlocker needs to know the network.

Is there any way to find what network this phone is locked to, other than trying a lot of other SIMs?

TIA

zcx