ring (somebody) back phrasal verb British English (
see also ring)
 to telephone someone again, or to telephone someone because you were not available when they telephoned you
 Synonym : call (somebody) back: 
 I’ll ring back as soon as I find out anything.
 I’ll ring back as soon as I find out anything. John rang, and he wants you to ring him back.
 John rang, and he wants you to ring him back.  [TahlilGaran] Dictionary of Contemporary English ▲