Interestingly, I just discovered that one could loan airtime worth of between 50 and 500 Naira on Airtel Nigeria network. A big thanks to a friend of mine who made this service (Airtel Advance Talk Time Service) known to me.
This is actually good especially on emergency whereby you may be out of reach of airtime recharge card access or ran out airtime in the night per say; I used it recently when there was nowhere to find a recharge card in the night.
Airtel Nigeria made it possible for subscribers to load airtime with a payback grace of four days