Iphone 3G version 4.1 SIM unlock

Hello,

I got a second hand Iphone 3G from Canada. and i was using it with my simcard normally. but when I upgraded to IOS version 4.1, it doesn't accept the simcard anymore. it says Invalid SIm.
I know it's stupid, but I tried to restore it back to its previous version. but now I lost everything (photos, videos, cotacts, sms etc) in my phone.

I would appreciate if you could help me in this regard.

Looking forward for your kind sooner reply,

Best regards,
Ashraf