iphone 5s will not use mobile data

I just started using the iphone 5s (unlocked) from Apple and everything works in Mascom Botswana except mobile data. I have settup my apn settings for Mascom and still get the error message "Could not activate cellular data network. You are not subscribed to a cellular data service." I however am subscribed to cellular data and when I check the amount of internet I have it is clearly not being used and available. I have tried restoring the phone, talking to Mascom, typing in different APN combinations found on the internet and nothing has worked. My roommate with an iphone 4 has no problem using the mobile internet here with his unlocked phone. What am I missing?