Why do mobile phones always receive multiple text messages?

Mine is annoying, too! Check online, China Mobile's explanation is:

90022 is the port between MMS center and SMS center, which is used to send the notification message "Did the receiver's mobile phone extract this MMS?" When the MMS center sends MMS to the receiver, this notification message (90022 port message) is invisible to the MMS mobile phone (the mobile phone does not display it), and the MMS will be automatically extracted immediately after receiving this notification message. When non-MMS mobile phone (or non-GPRS mobile phone) receives this message, the notification message on port 90022 will be displayed as garbled or empty message.