By mistake, someone changed my birth year and bow am locked for being under age. I want to delete my account now and make a new one. But I can't get access to the option as it shows me the note always I log in.
Contact whomever you have the account with. (Which, as an aside.... how the hell are we supposed to help you when you don't even tell us what account it is? Like seriously?)
We can't help with this matter anyway by the rules and as a simple matter of practicality - we don't control their systems or have any sort of privileged access. Go to the support pages for whoever services this mystery account of yours and see if they can help you.