Hi, I have to unlock a german iphone 3gs running ios 5.1.1 with baseband 05.16.05 ...
I have read a lot of threads, but don't find anything..

How can I do the unlock? Thanks

Up!........

Please search the forum before posting. This question has been asked hundreds of times and all these threads do is serve as a spam honeypot for shady unlocking websites that never work reliably.

You can upgrade to the iPad baseband and then downgrade to an unlockable baseband by using redsn0w. The only time this wouldn't work (and you shouldn't attempt it) is if the 3rd - 5th digits of your iPhone's serial number are 134 or higher -- these models have a different baseband chip that will be bricked (permanently) by attempting.

Closing thread, there are others that detail this process.