There are three types of 400 telephones: 4000 (Unicom), 400 1 (mobile), 4006 (Unicom), 4007 (mobile), 4008 (telegraph) and 4009 (telegraph).
The process here is as follows: a copy of one of the three certificates (enterprise business license, tax registration certificate, or organization code certificate) is stamped with official seal+copy of ID card+contract agreement.