New 3g to me -Invalid sim on at&t Help!

[Iman2011]

I just purchased a used 3G 8gb iphone and it appears to be jailbroken and unlocked. It has cydia on I and something called installous. I activated a new Go Phone sim as I did when I first tried the go phone sim idea on my other 3g 16gb iphone phone however this time when I put in the sim card after I activated it online , I get invalid sim on this 3g 8gb phone. Read alot of blogs but have yet to find a definitive reason for the issue, any help would be greatly appreciated. Thanks

 

[jekyoo]

Check if it's unlocked.

Only 04.26.08 (3.0) , 5.11.07 (3.1.2), 5.12.01 (3.1.3), 05.13.04 (4.0) and 06.15.00 (iPad baseband) are unlockable. If it's none of those, you'll need to flash the iPad baseband into the 3G using redsn0w.

 

[Iman2011]

Its a iphone so all at&t cards should work correct? I have another iphone that is not unlocked and it will take the go phone sim but not this one. Can't figure it out, thanks

 

[Iman2011]

anyone? still have this problem

 

[Applejuiced]

You didnt activate the gophone sim with another cellphone right? Cause I know AT&T sims are locked to the particular cellphone.

 

[Iman2011]

Nope just activated online like I did the last time when I got my first iphone and that one works perfect, I just picked up 2 more iphones, one 3g stock and one 3gs supposedly unlocked and they also are also showing invalid sim. Whats weird is I can put the either of the go phone sims in my 16gb stock iphone and both works perfectly, get a signal right away (less then 10 seconds) but each time i switch them to any of these other phone its either no service or invalid sim?? Both sims where activated online. Just want to find out whats going on with these iphones as I need to get at least one of them working but in reality they all should work with at&t go phone sims should'nt they? Again any help would be so much appreciated.