400电话是一种主被叫分摊业务，即主叫承担市话接入费，被叫承担所有来电接听费用。目前已广泛用于多行业售前售后服务咨询方面。400电话分为4006（中国联通），4007（中国移动原铁通），4008（中国电信），4001（中国移动新号段），4000（中国联通新号段），4009（中国电信新号段）。
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电话是专为企事业单位设计的全国范围内号码统一的虚拟电话总机，所有拨往400总机号码的来电均被转接至预先设定的固定电话、手机或呼叫中心专线上。400电话总机只负责处理呼入的电话，不能外拨。话费由企业和拨打400电话的用户分摊，拨打方仅支付当地市话费。400热线体现了企业服务意识，是信誉和实力的象征。
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.