Hello Mohd Umair Ansari,
The issue pertains to a tenant lockout scenario, where you are unable to log into the Azure Portal due to an incomplete MFA process and there are no other global admins in your affected tenant to revoke your current MFA sessions and then re-register MFA on your new mobile device. However, since you mentioned that you are the only Global Admin in your tenant, this qualifies as a tenant lockout scenario.
To resolve this issue, we have engaged our Data Protection team through a support ticket. They will reach out to you via email or phone to help restore access to the tenant and assist you in resolving this issue.
I have given the support ticket details over the Private Message for your reference.
Once the issue has been resolved by our support team, please feel free to revisit here and kindly click "Accept Answer", and "Upvote it" as this will be helpful to other community members facing similar issues.