Q: bought a phone that is still linked to the owners itunes but owner not available to reset

You can sign out of the AppleID: Sign in with a different Apple ID on your iPhone, iPad, or iPod touch  - Apple Support

If the device has Find My iPhone Activation Lock enabled and you don't have the password, then you'll need the original proof of purchase (invoice/receipt) for the device and will need to contact Apple.  If you don't have the original invoice then talking to the original owner (person you bought it from) is the only option.

Best of luck,

Madison