I am unable to delete a group email

I created a group but after deleting the group it continues to show up as a group in certain places even when it no longer exists. When I go to remove it from the user it is still "stuck to" it tells me " You are not authorized to perform this operation ". Additionally I cannot use the email it was created under as it still thinks its there somehow.

I want to re-use the email extension the group was under for something else. Is there some way to remove this phantom group?