How can I reject certain messages starting with a specified telephone number prefix?
You have to configure the outbound routing table. If you want to prevent your customers to send messages to certain destinations, you have to setup a “dummy service provider connection”. For this purpose an HTTP server SMS service provider connection is a good choice. After this connection is setup, you should add a new rule to the outbound routing table, that will route messages with the defined prefix to this dummy service provider connection. This way messages, that are destined for the defined destination, will not go to your normal SMS service provider connection. Instead they will be routed to this dummy connection and they will be dropped. To specify the prefix, when you create the new rule in the outbound routing table, you should define Condition 2 (Recipient phone number). This condition should match be a regular expression, that matches your telephone number prefix. For example if you wish to prevent messages to be sent to prefix 123, put the following pattern into the field
