I've been using a modded iphone for the last 6 months & am currently in the process of changing my mobile provider.

However, every time I insert a new SIM card I get 'No Service'. When I insert my original SIM it works fine.

I'm currently using T-Mobile (UK) and have tried the following SIM's:

O2, Vodafone UK, Orange, Asda Mobile

I'm currently on version 2.1 (5F136) of the firmware.

I've even tried restoring & doing a complete new mod but no joy.....anyone able to offer any advice?

modded iphone ? Do you mean an unlocked iphone?
If so, put in the SIM and try reset network settings.

Yes its an unlocked iphone & has been since June this year.

I've tried to force the right network for the new SIM but get a 'restricted network' warning.

Not sure if you're from the UK dtube but the official network provider is O2, I'm currently on T-Mobile & am moving onto Vodafone UK.

I've done a full restore & quickpwn but still get no joy other than my original T-Mobile.

use quickpwn to unlock again

Originally Posted by lordofdaflies

use quickpwn to unlock again

Have done that LODF (with the new SIM installed) - any other suggestions?

I had similar problems and tried qwkpwn with no success initially. It wasn't until I did a restore through itunes but disconnected when it asked me to activate that qwkpwn worked successfully. I did this with my vodaphone card in, works perfectly. Have tried other network cards in since unlock and they all appear to work fine except 3. So give it a go, just don't let itunes activate the phone

Download bootloader from cydia and unlock.........

OR

Try a DFU restore and quickpwn