Hi, I am Dhanam, Independent Advisor here to work with you on this issue.
I know this has been difficult for you, Rest assured, I'm going to do my best to help you.
Its only for under 18, if you are 18 plus, you don't need to get permission from others.
You may change your birthday using the following link: https://support.microsoft.com/en-us/account-bil...
For most people, in most regions
Sign in to Your info on the Microsoft account website. https://account.microsoft.com/account/Account?r...
Select Edit your personal info.
Change your birthdate, and select Save.
Also refer this page:
https://answers.microsoft.com/en-us/skype/forum...
This is a public user-to-user support forum. I'm a user like you helping other users. I do not work for Microsoft and do not have access to any user accounts.
I hope this can help you. If this still can't solve your problem, just let me know and I'll do my best to try to help you.
Regards
Dhanam