customer service vs usage

customer service

noun
  • The act of providing services to customers before, during and after a purchase. 

  • A department that provides services to existing customers. 

usage

noun
  • The act of using something; use, employment. 

  • Custom, tradition. 

  • The established custom of using language; the ways and contexts in which spoken and written words are used, especially by a certain group of people or in a certain region. 

  • A custom or established practice. 

How often have the words customer service and usage occurred in a corpus of books? (source: Google Ngram Viewer )