Someone said they could extend my account if I gave them my keycode, and I did.

Was this someone you connected with online?  If you weren't talking to our technical support directly, it isn't likely that this is legitimate.  If you get any notices in the future about your keycode being installed on too many machines, then it is likely that this person is using your keycode to install on their machines, or is selling it online.  If that happens please let me know and we can deactivate that keycode and re-issue you a new one.