Emails linked to phone number

it says that i have to enter my email or phone number and my phone number is linked to an other account

Is the account linked to another email/phone number?

Hi and thanks for reaching Microsoft Xbox gamer's community. My name is Josef.
I'm an Independent Advisor and a Microsoft Xbox user like you.

Hope you're doing great today Betin

If your roblox account is linked to your Microsoft account and you don't remember anything about email or phone numbers possibly linked to it

You need to recover the account filling this form:

https://account.live.com/acsr

Sadly, an account cannot be recovered with the gamertag alone.

Thanks for your reply. I tried the recovery form but the first step wants the email or phone number linked with the account and ive tried both but it says theyre not linked to an account even though i was able to use the same phone number to find which
email was linked!

The best thing I would suggest you to do is to add a phone number or an alternative email address on the accounts. It can be your phone number and email. This way if you forget the kid account email address or password, you can use your phone or email to receive a reset link and will not even need the recovery form.