Let’s assume you borrowed 100naira from MTN and you used up the credit,your are now left with only 0.00naira, remember that if you recharge 100naira they will deduct the 100naira meaning that you just paid the amount you borrowed. To avoid loosing the 100naira airtime. The default code for Recharging on MTN Sim is *556# soinstead of Using the Default pin Kindly by dialing *885*Your Recharge Pin#e.g*885*123456781245# With this you have automatically paid for the 100naira you borrowed and still left with 100naira Bonus. NOTE:-The same Process is applicable to any amount you borrowed from MTN. Also note that normally when you recharge with *885* it doubles the amount you recharge.