Activating my iPhone...

That is almost always because the phone was hacked or jailbroken to unlock it.

It doesn't matter who did it. The phone was jailbroken. You can not get help here.

Discussing jailbroken and hacked phones is forbidden by the terms of service here.

I imagine by now you've seen what jailbreaking causes. Since you didn't do it, you probably didn't want it jailbroken in the first place. So this may help you out: http://support.apple.com/kb/HT1808. This discusses Recovery Mode, which is probably necessary to restore your device to a working state since it was jailbroken.

You will need to contact AppleCare and give them the serial and model number of your iPhone and find out which cell carrrier it is now locked with. Contact that carrier and see what their process is for unlocking and whether they will let you do it. If yes, complete the process then activate. If you get this far you may have to take one more step which will require you to use Google.

i will never spend my money again to something like this where i even can't get helped...

You have to understand that you have a hacked phone, which is the reason you can't be helped. Jailbreaking violates the iPhone's end user license agreement, so Apple can (and will) deny service for it. We are all users here but Apple hosts the forum.

Frankly I think that those who jailbroke are in over their heads, so I wouldn't help them anyway. But I also understand that you weren't the one who did it, which is why I provided you instructions.

Maybe you should try buying phones from legitimate sources instead of on the gray market. Neither the 3G, nor the 3GS are available for sale from any legitimate source any more. They are both discontinued. Buy a phone directly from Apple or from a carrier that is authorized to carry them.

It's not our fault, or Apple's, that you have decided to go 'off the grid' and buy high end electronics form what amounts to the back of a van in a mall parking lot.

What did you expect was going to happen? TANSTAAFL

Your argument says that no one should EVER buy a used iPhone. Yet a lot of recommendations here to people are they should sell their iPhone on the open market to get a better price, or sell their locked iPhone to get a truly unlocked iPhone from a legitimate source (which might not be available where they live). You have no idea where they bought their iPhone from.

They didn't expect a free lunch, they just wanted an iPhone, even if they had to buy a used one. This problem will clear itself up, at least for GSM iPhones in the future since AT&T began unlocking iPhones (I unlocked my iPhone 4 before I gave mine away) and people selling them can unlock them prior to the sale.

Which is a good thing for Apple since their presence in developing countries is poor and dropping.

You most likely will not solve your problem with Recovery Mode; you will have to try to officially unlock it or wait for an alternative solution.

Follow the instructions in my previous post.