@Ng Chun Siong
Thank you for your post!
When it comes to the third party app, are you able to share which app you're using? If you're using the Microsoft Authenticator app and want to remove your account, you can follow our - Remove account from app documentation.
Removing the app from your device:
- To remove the app from a device using a personal Microsoft account. Go to the two-step verification area of your Account Security page and choose to turn off verification for your old device.
- To remove the app from a device using a work or school Microsoft account. Go to the two-step verification area of either your MyApps page or your organization's custom portal to turn off verification for your old device.
If you have any other questions, please let me know.
Thank you for your time and patience throughout this issue.
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