Unable To Delete An Address From My Contact List (think their email has been hacked)

I have been receiving what should be junk mail in my Outlook inbox.  I have repeatedly tried to ban the address without success.  Today I was cleaning up my contact list and found one name which could not be deleted nor could I edit any info for this name/address.  I believe this person's account is the portal for my receiving these unauthorized mailings, and this email acct may have been hacked.  Any suggestions how to remove this name or correct this problem?  Thanks!