i need to turn off find my iphone on my computer

The repucussions are bad, you may not want to do.

You have removed the device from your account after you erase it, Activation Lock will be turned off. This allows another person to turn on and use your device. If you're using iCloud and Find My [device] on the device, sign in to iCloud.com/find or the Find My app on another device, select the device, and click Erase. After the device has been erased, click Remove from Account. This will turn off Find My.

Why you have not been able to turn it off on your iPhone is not clear to me.