Dear noor e alam chowdhury,
Thank you for posting in the Microsoft community.
I understand that you are trying to help your brother recover his account, and I also know that this account is very important to him.
If he has always been in the area where the account was created, and the account is locked with a "This verification method is unavailable" prompt, he should try using a different device, such as a mobile phone. Switch to mobile data (not Wi-Fi), then log in to account.live.com and attempt to verify with the mobile phone number again.
If the account is shown as locked when trying to log in on any device or with any mobile phone number, this issue may take some time to resolve. He should wait for a week, then log in to the account again and try to unlock it. During this period, he should refrain from sending any more login requests to the server.
The above are the common recovery methods I know. If all these attempts have been made without success, as a last resort, I suggest contacting the live chat support to inquire whether the account can be recovered by submitting more additional information.
Here are the specific steps to contact the live chat support:
(If the following steps don't display as expected, please try changing your browser and doing it one or two more times.)
- Sign in to this link using any personal Microsoft account:Contact - Microsoft Support. Type "account recovery" into the search box.
- Click "Sign in and contact support" at the bottom of the page.
- Under "Products and Services", select "Microsoft 365 and Office".
- Under "Category", select "Manage Account Security"/ “Technical Support”.
- Click "Chat with a support agent". Then fill out the contact information so that the online agent can contact you.
Please note:
- Online chat does not support enterprise accounts. If you currently do not have an available personal account, please create a new @outlook.com account to use.
- the online chat service is available during working hours on local business days.
We appreciate you spend your time working on this issue. I wish you all the best.
Best Regards,
Ulrica.W - MSFT | Microsoft Community Support Specialist