Somebody hacked into my account and changed my name. My account name was damianea103. But it's DonkeyPrecum. I can't change it unless I wait 30 days. And I don't wanna go online with that username. How do I change it (or at least contact Mojang to change it for me)?
If you have your web browser to save passwords (or any web browser not on your own computer you used to log into Minecraft's / Mojang's website), you may have had someone else do it easily that way. Also, I would always recommend you never log into any account you are wanting to keep on any computer that isn't yours... ... and never ever trust a not-well-known Minecraft launcher (and totally not a hack client -- those have been known to steal logins and/or infect the system you run it on).
EDIT: Like someone responded to you by comment there, if you have the proof still that you purchased the account, use that when requested by Mojang support.