keeps calling no one on the other end

Got the call but no one else on the other end!

Try to call the number back and it says call can't be completed as dialed.

Shows up on caller ID as "DIR ASST MI" or something similar.  We get periodic calls ID'd as Directory Assistance from Michigan, Ohio, and California.  From what I've seen on similar calls on this site and others, this is the old "I'm from Microsoft and we've found something evil on your computer" scam.   At any rate, a 555 exchange is bogus (this is why movies tend to use 555 as a phone number) and, more importantly, Directory Assistance from anywhere is not going to call to say "Hi".

Good information; thank you Lucky.