My old(it's only my old account because one day I got logged out and could never log back...

That's the thing the phone number and recovery email were changed.

Hello, first it's a pleasure to be able to help you today.

My name is welcome to the community.

Hello Mei, I'm sorry about what happened to your account but to recover your account, you must complete the account recovery form below.

Recover your account

https://account.live.com/acsr

Help with the Microsoft account recovery form

https://support.microsoft.com/en-us/account-bil...

Hello again, despite exchanging the email and name, you should try to recover your account through the form, or contact Xbox support and request an "ATO" (Account Takeover)

Well, I don't need to change my gamertag for my new (accidentally) created account. I just need to log back into my old xbox account.

And if I try to use my old gamertag, it says that it's already used. Trying to add a # makes it say that I need to have 12 characters or less.

My email doesn't access 2 accounts, it only accesses the new one and I can't log back into my old one.

No, sorry if there's a misunderstanding.

What i wish to do is to transfer my old Gamertag ( 4+ year old account) to a new WLID account that i created. I can still log into Xbox live from the Xbox console, however the system asks me to log in my old WLID password before i can make the WLID change,
but i can't since the account is locked.

The reason my old WLID got blocked was because apparently someone tried to log in too many times using a wrong password.