400電話是一種主被叫分攤業務，即主叫承擔市話接入費，被叫承擔所有來電接聽費用。目前已廣泛用于多行業售前售后服務咨詢方面。400電話分為4006（中國聯通），4007（中國移動原鐵通），4008（中國電信），4001（中國移動新號段），4000（中國聯通新號段），4009（中國電信新號段）。
400 call is a kind of call sharing service, that is, the caller bears the local call access fee, and the called bears all the call answering fees. At present, it has been widely used in multi industry pre-sale and after-sale service consultation. 400 telephones are divided into 4006 (China Unicom), 4007 (China Mobile former China Railcom), 4008 (China Telecom), 4001 (China Mobile new signal section), 4000 (China Unicom new signal section), 4009 (China Telecom New signal section).
400電話是專為企事業單位設計的全國范圍內號碼統一的虛擬電話總機，所有撥往400總機號碼的來電均被轉接至預先設定的固定電話、手機或呼叫中心專線上。400電話總機只負責處理呼入的電話，不能外撥。話費由企業和撥打400電話的用戶分攤，撥打方僅支付當地市話費。400熱線體現了企業服務意識，是信譽和實力的象征。
400 telephone is a virtual telephone switchboard specially designed for enterprises and institutions with unified number nationwide. All calls to 400 switchboard number are transferred to preset fixed telephone, mobile phone or call center line. The 400 switchboard is only responsible for handling incoming calls, not outgoing calls. The call fee is shared by the enterprise and the user who dials 400 calls, and the caller only pays the local city call fee. The 400 hotline embodies the service consciousness of the enterprise and is a symbol of reputation and strength.