Using iphone 4 to get a data bundle?

How much is 75mb of data for a iphone & how long would it last me? (In Africa)

75 mb is not that much. Most songs are about 5-10 mb. Apps range from 5-40 or more mb, so as I'm showing it'd be easy to go over that amount. I'd say you'd could go over it within a week depending on what you use. If you are a music and apps person a week. If you are more of an occasional internet and social media browser I'd say you could stretch it 2 weeks.