I don't know how, but my IMEI was changed.
Do you know how to put back original (which is on bak side of the case)?

you CANNOT accidentally change the IMEI number!! plus it is alo illegal to. also since the iphone is so new its unlikely that a hack to change it has been developed yet.

how did you buy your iphone? the most likely way it doesn;t match the IMEI number on the outside is that the back case has been replaced, with an incorrect one.

I bought it brand new in applestore. Still hour ago I had same numbers on back case and in the system.
I don't know how it happend, but it happend during process with iactivator

deactivate it then check your imei again...

how should I deactivate it?

use iPhoneActivationTool or something to deactivate. search...

i would try doing a full system restore

even full recovary didn't helped.
And iPhone ask me for inserting proper SIM (probably he has insight some algorithm about checking IMEI and ICCID).
I am lost. Probably will call Apple, but I don't know what I will say them.

Any other idea how to put my IMEI back?

I have the same problem !!!! Identically. I have lost all the night widthout close eyes. My process is:

1) Phone Totally unlocked with GeoHot process with 1.0 firmware.
2) Power + Home key for totally upgrade of firmware to 1.02.
3) Many try to be activate 1.02 with wrong version of jackbreak relese
4) Iactivator 1.1.4 on Mac

I don't know when iphone have changed IMEI and Referrer of the Lock Provider. Now it not accept any sim included the AT SIM. And for end is also locked !!! I can only activate it. There is something that have caused it.

Please post your tryed and when you have discovery IMEI changed. My Actually IMEI begin to 0049....

Post reply i don't know ad i can recovery this. If IMEI is in my backup of NORDump or other. Attention to all.

absolutly same as linusmax describe, only difference, that I spend 2nd night
I checked thread mentioned above, understand, where that patch is stored, but still don't understand why my IMEI was changed?
It supposed to be same, why is unique to phone and is recognised by Network Operator during signing process with your SIM. ICCID is unique number of your SIM card related with your Operator DB.
Also how should be IMEI changed and pass final step of geohack?
Will wait over night for US comunity and will see.
Must check with people, who passed geohack if their IMEI is same.