how do I disconnect my phone from computer

Hi alpine1019,

Thanks for reaching out in Apple Support Communities. I understand you'd like to know how to disconnect your iPhone from your Mac. I can understand why you'd reach out for more information on this; I'd like to help. Disconnecting your iPhone from your Mac depends on the features you're using to connect them. If you're referring to features such as calls or messages going to your Mac you can disable them using these steps:

• For calls tap Settings > Phone > Calls on Other Devices; disable the feature or deselect specific devices as needed.
• For text messages tap Settings > Messages > Text Message Forwarding, disable any devices you don't want receiving your texts.

Other features that can be linked are mentioned in the following resource and would need to be disabled if you're using them: Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch

Lastly, there are some features that connect your iPhone and Mac via iCloud such as, Contacts, Calendars, Reminders, iCloud Drive, Photos and others; you can disable these features in System Preferences > iCloud, or System Preferences > Apple ID, depending on your macOS version. If you'd like to stop using the iCloud account you use on your iPhone with your Mac, you'll need to sign out through System Preferences.

If you're referring to a different way of disconnecting your iPhone from your Mac, let me know.

Best Regards.

When iPhone and Mac are signed in with same Apple ID and password on the same network to disconnect iPhone from Mac you need to sign out the Apple ID from an iPhone see the article https://support.apple.com/en-in/HT208242

If you'd like to stop using the iCloud account you use on your iPhone with your Mac, you'll need to sign out through System Preferences.

The device to be disconnected is an iPhone , if Apple ID is signed out from Mac system preferences > iCloud the Mac will be signed out from iCloud account and not the iPhone .

As Apple ID is just a syncing process , say if there are many apple devices like iPhones , few Macs in an office and all are signed in with same Apple ID and password , a person signs out from Mac so all people who are synced with Mac will get signed out from their devices .

So any person can give command to sign out from his device , all the devices will be disconnected and signed out from their Apple ID account ( its not true ) and its like controlling the devices .

In very short Apple ID sign out process is to sign out from individual device .

Also op has not mentioned what is the way he has connected an iPhone and Mac like though usb cable , continuity feature ..etc