百問不厭，百拿不煩 [－问－厌－－－－烦]

Jyutping baak3 man6 bat1 jim3 ， baak3 naa4 bat1 faan4
Pinyin bǎi wèn bù yàn ， bǎi ná bù fán

Definitions (Wiktionary)
  1. phrase, idiomatic
    to patiently answer the customer's questions and show them the goods they want; to serve the customers patiently and tirelessly (of a shop assistant)