How do I unlink my iPhone from another Apple Account?

Linked how? Where?

What account? An Apple ID account? A Phone service account? An email account?

What exactly is the issue?

Where are you seeing this account?

click here ➜ Writing an effective Apple Support Communities Question - Apple Community

So now your phone is activation locked to an Apple account you no longer have access to.

There are only 2 options.

A: Regain access to that Apple account so that you can sign out of it on the device and start over.

B: Provide the original proof of purchase from Apple or an authorized retailer to Apple to have the activation lock removed.

How to remove Activation Lock - Apple Support

If you can't do either one of those, the device is effectively a brick.

There is no way to bypass the activation lock. You need the credentials for the account used to lock it or proof of purchase.

I'm going to take a wild guess and say you restored a backup made from your old company phone to your new personal phone, resulting in the new phone being locked to an old company linked Apple account that you no longer have access to...

Is that correct?

yes i did restore the backup from my old company phone

And that.......is the issue.

I have not run into this issue myself, so hopefully KiltedTim will have more details for you on what...if anything....you can do about this.

Are you referring to Mobile Device Managment, which means your device is managed by your previous employer? If so, you need to contact your previous employer to get rid of it. otherwise, please elaborate.

What kind of account are you referring to? Are you referring to an email account, an Apple Account, what exactly. Please provide more detailed information to help people to troubleshoot this issue.

Try tap Settings > General > VPN & Device Management

What do you see on the screen? A screenshot would be really helpful if possible.