There are some people who don't know how to check their MTN extra Bonus Credit and MB on their phone but i will tell you how to check it if you are one of those who don't know how to find out when mtn gives them free MB or Free call credit.
I was chatting with one of my friend and he told me that he browse free with Opera-mini because when ever he browses his money will not be deducted but i told him that MTN gave him Free Internet MB bonus but i was surprise that he don't even know how to check MTN Extra Bonus Credit or free MB and that is why i decided to show those who don't know how to check it, how to do it.
Sometimes you might even be making calls for free without knowing why your money is not being deducted but the answer is that mtn just gave you extra call credit bonus.
To check MTN Extra Bonus Credit and MB kindly dial *559*2# *559*3# for sms bonuses or *559*4# for extra bonus etc you will see if you have been rewarded by mtn with free MB or extra credit.
Hope it helps