What business can China Unicom send so many short messages for free every month?

Hello, China Unicom has these SMS packages:

16 yuan Package:

No monthly rent

● No caller ID fee is charged.

● When the local telephone line is busy (Monday to Friday 09: 00-1:00 and 19: 00-2 1: 00), 0.27 yuan/minute; Leisure time (other times and legal holidays) 0. 1 yuan/minute; Local call is free; Local originating toll 0.3 yuan/min.

● Other charges are charged according to standard charges.

● 16 yuan 250 SMS messages (including intra-network and inter-network SMS messages, SMS monitoring and Unicom incoming SMS messages) and caller ID fee.

26 yuan bag:

No monthly rent

● No caller ID fee is charged.

● When the local telephone line is busy (Monday to Friday 09: 00-1:00 and 19: 00-2 1: 00), 0.27 yuan/minute; Leisure time (other times and legal holidays) 0. 1 yuan/minute; Local call is free; Local originating toll 0.3 yuan/min.

● Other charges are charged according to standard charges.

26 yuan package 550 short messages (including intra-network and inter-network short messages, short message monitoring and uplink short messages of China Unicom) and caller ID fee.

39 yuan bag:

No monthly rent

● No caller ID fee is charged.

● When the local telephone line is busy (Monday to Friday 09: 00-1:00 and 19: 00-2 1: 00), 0.27 yuan/minute; Leisure time (other times and legal holidays) 0. 1 yuan/minute; Local call is free; Local originating toll 0.3 yuan/min.

● Other charges are charged according to standard charges.

●39 yuan Package contains 650 short messages (including in-network and inter-network short messages, short message listening and incoming short messages from China Unicom), as well as caller ID fee, ringtone and function usage fee of10/93.

No monthly rent

49 yuan bag:

● No caller ID fee is charged.

● When the local telephone line is busy (Monday to Friday 09: 00-1:00 and 19: 00-2 1: 00), 0.27 yuan/minute; Leisure time (other times and legal holidays) 0. 1 yuan/minute; Local call is free; Local originating toll 0.3 yuan/min.

● Other charges are charged according to standard charges.

49 yuan package contains 900 short messages (including in-network and inter-network short messages, short message listening and incoming short messages from China Unicom), as well as caller ID fee, ringtone and function usage fee 10 193.