hi, i have a problem to sync my 32gb 3gs iphone(us set)

well i accidentally Update my phone with itunes from 3.0.1 to 3.1fw, and i lose my UNLOCK

so i couldnt downgrade to 3.0.1..and my phone was stuck at the emergence call mode

so i brought back to the seller and he help me open back the menu so i can use it like a ipod touch,
because there is no unlock for the 3gs on 3.1fw with baseband 05.11.07 yet.

so he did help me open the menu, and i test it( able to take photo,play games, connect to wifi)
he install lots of games and apps into my iphone tooo ~

just not unlock

then at home
i was trying to sync MORE movie or song or apps to my iphone with Itunes

but then it sed "please insert a simcard to activate ur iphone..in order to sync it"



I WONDER WHYYY!!!!

tat guy able to put apps into my iphone,
bt why cant i sync it with itunes???


MY 3gs iphone is :

ON 3.1fw((7C144)

modem fw: 05.11.07

cydia is installed in my IPHONE

then at cydia home has a " this device has a 3.1 ECID SHSH on file"


so anyone can help me with my problem???