To deactivate call barring from a phone on the MTN network, press "#330* " followed by a personal barring code and the "#" key. Once this has been entered, press the "Send" key.
It is also possible to deactivate call barring on incoming or outgoing calls only. Barring international or roaming calls reduces the risk of these calls being made and increasing the monthly bill for the service. If it is necessary to place an international or roaming call, the barring can be deactivated. The default call barring code for MTN is 0000. When in use, call barring prevents calls completely. They are not merely routed to voice mail.