It means nothing, other than that he hasn't called you back. You have NO information on which to base any further conclusion.
Yes. HR people never call back.
It means he wasn't able to come to the phone when you called. Relax.
It's either then you called me or I'll call you later
call him back later and if he doesn't pick up don't call back
no you should not
called back.Call back is a phrasal verb. When changing to past only the form of the verb call changes. The adverb back remians the same.
Usually, not being "called back" by a hospital after running diagnostic tests is a good sign, meaning the tests were negative.
5 to ten hours
It's called
He tried to call her several times. He called her several times.
He/she is called back to speak again;)
The hours you called out are exactly 24 hours during the work shifts.