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 product
售后服务