Group members not removed from joomla users

Hi Tuan

I have discovered that when a 'Group Member' is removed by the Group Admin, their Joomla user is not deleted.
Also, for some reason the Group Admin can no longer add further group members if their limit is reached

For example

• Limit of group members is set to 20
• Group Admin has at some point set up 20 group members
• But since deleted 5 group members
• The 5 deleted group members still have a login via the Joomla user system
• the Group Admin can not add any more group members (event though technically they only have 15 setup)

I hope that makes sense.
Can you help please as, obviously, we do not want people to have access to the site once they are removed.

Thanks
Alison