I ain't too sure but have you tried here?

http://onigiri.cyberstep.com/charge

What's wrong? I get sms with code to write. I wrote in game to System > Serial Code and I see: The serial code does not exist.
Maybe this is wrong place. Where I can write that code? Help ;/

Yes. I bought exactly here. SMS Mobile ZONG

You can try to input the serial code later or if the problem still persists then, you can go report it to them over here:
https://www.cyberstep.com/help/mailform/billing

Thanks for help, but now i see An error has occured..