How to send please call me on mtn

Please call me on MTN allows you to send an SMS asking that person to call you. The service is free of charge.
How to send please call me on mtn.  Are you out of airtime and you really need to call and speak to someone.

To send a CallBack. Dial *121*(cellphone number)#, e.g., *121*0760 123 4567#
Press the send or call button.
To personalise your CallBack SMS. Dial *121# to add your name and access other features