I've just bought a Nokia 7600 which I've had unlocked. I am using my Orange contract sim but I am struggling to get a signal. I believe it may have something to do with the phone currently using the UMTS network. I would like to use the GSM 900/1800 network but the option to switch networks in the phone is disabled. Any ideas??

It's a 3G phone so you might run into difficulties. However there is a thread running somewhere about how to get 3G phones working on 2G networks with 2G sims. I don't know which thread it is but I'm sure you'll be able to find it easily enough.

Very Quickly, unlocking is not enough - you need to get the factory settings flashed and this will allow you to access a previously hidden "Network Options" menu that'll allow you to choose 'GSM only'.

I've spent most of this week doing the same as you, but only on vodafone - for me mum!

Thanks for the advice, what is the best way to go about this? Can you reccommend anywhere I could get this done?

Where did you buy it from? Take it back saying it's crashing, freezing and rebooting a lot, and they should send it in for a firmware upgrade. Carphone warehouse are easy to persuade to do this.

Or join Club Nokia and take it to an autherised Club Nokia dealer (there's one in most towns and cities) and they should be able to do it on the spot for you, for free. If you aren't a member then they are normally less helpful.