@Sumit kumar Shaw , Thanks for posting in Q&A.
To remove the company portal on Android, you can try the methods in the following link:
https://www.lifewire.com/delete-apps-on-android-phone-5271421#:~:text=Here%27s%20how%3A%201%20Open%20Settings%20.%202%20Select,5%20Confirm%20you%20want%20to%20uninstall%20the%20app.
Note: Non-Microsoft link, just for the reference.
If you want to unenroll your device from the previous organization, and now you account is not available. the only method I can think is that you need to contact your Intune admin in the old company to remove the device in Intune portal.
Hope it can help.
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