call in vs ring back

call in

verb
  • To report; communicate (a message) by telephone or similar. 

  • To communicate with a base etc, by telephone. 

  • To pay a short visit. 

  • To summon someone, especially for help or advice. 

  • To withdraw something from sale or circulation. 

ring back

verb
  • To return a phone call. 

  • To make another phone call to the same person. 

How often have the words call in and ring back occurred in a corpus of books? (source: Google Ngram Viewer )