It's not new that MTN give you #500 when you use #100 per day and the #500 bonus also expire at 12 O'clock that Mid-night.
If you use N100 Credit, You get N500 Bonus. If you Exhaust N200 you
get N1000. You need to first dial *507# and make sure you receive
confirmation sms to enjoy the bonus as you used N100 recharge card.
=> Now to get N500 with N2 make sure you are on MTN Zone [Dial
*135*1# to migrate to MTN Zone] and make sure that you have minimum of
#2 on your phone.
Wake up any time after 12 O'clock at mid night and call any number
[MTN] Use the N2 and you we be given a N500 Bonus that you can use to
call all MTN Numbers through out that day.