after-sales service
noun /ˌɑːftə ˌseɪlz ˈsɜːvɪs/
  /ˌæftər ˌseɪlz ˈsɜːrvɪs/
 [uncountable]- the fact of providing help to customers after they have bought a product, usually involving doing repairs that are needed or giving advice on how to use the productTopics Suggestions and advicec1