Since the introduction of Do-Not-Disturb service across all GSM Networks in July, 2016, there has been lots of complaints by many GSM subscribers. The bulk of these subscribers had DND activated on their lines by the GSM operators without their consent.
An attempt to deactivate DND from their lines with the normal codes provided proved abortive because the system returns a response saying the lines are not on DND. In this case, the simple work around is to manually activate then deactivate DND from the line.
Below is a list showing the various DND Deactivation codes for the GSM networks.
For MTN lines, text ALLOW to 2442.
For AIRTEL lines, text ALLOW to 2442.
For GLO lines, text ALLOW to 2442.
For ETISALAT lines, text START to 2442.