MTN subscribers will now be receiving SMS on how to top up airtime directly from their bank accounts effective August 3, 2017.

MTN On Demand is a service which allows subscribers to buy airtime directly from their bank accounts via a code at their convenience, anytime, anywhere. Subscribers can buy airtime to a maximum of N3000.

Now, MTN customers will receive the SMS when they perform any of the activities below:
1. While on a call and their balance goes below N50
2. When they are about to initiate a call when their balance is between N0 and N50

Example of the type of SMS MTN customers will receive:

“You can now top up your airtime count directly from your bank. To top up, dial *904*airtime”

http://www.tellforceblog.com/2017/08/mtn-launches-automated-on-demand.html