If you've run out of credit, need to make a call and can't get to a shop, you can always send a free SMS message requesting others to call you back even when you do not have any credit to make that important call. It's so convenient.
Usage
Just input *126*786xxxxxx# (where "786xxxxxx" is the number of the
receiver) and press the send key. A message requesting the other person to call you back will be sent immediately.
Please refer to your mobile handset's user guide to activate this useful service.
