How to Contribute on behalf of an individual instead of organisation for Member Dues?
You can do so by adding query parameter cid=0 in the url
So if the url is
/civicrm/?civiwp=CiviCRM&amp;q=civicrm/Fcontribute/transact&amp;reset=1&amp;id=10

You need to add cid=0 to the url as shown below
/civicrm/?civiwp=CiviCRM&amp;q=civicrm/Fcontribute/transact&amp;cid=0&amp;reset=1&amp;id=10