Iphone 3G on MTN no internet

[veect]

Hi

I received an Iphone 3g from a buddy of mine while my phone is in for repairs.
The problem is that the phone cannot establish a internet connection using an MTN sim.
When i insert a CellC sim in it, it works fine Safari and whatever other app that is dependant on
the internet connection works

I tried the following APN's already

myMTN
internet

Also tried this from MTN's site :

http://www.mtn.co.za/Support/PhoneandModemSupport/Pages/default.aspx

The weird thing is that when i insert the CellC sim the menu under mobile data has way more options like MMS and other options for the internet APN.

I am very new to Apple

Any advice will really be appreciated