MTN recently launched their own branded Android phones MTN Smart (Sm@rt) Minis. Here's a guide on how to root them.
How to Root MTN Smart (Sm@rt) Mini S620 and S720i
Procedure
1. Download Vroot (Also known as Root Master)
2. Enable USB Debugging on the phone (Settings > Developer OR Settings > About > Keep clicking Build Number > Back to Settings > Developer)
2b. Install PdaNet on the PC with phone connected to PC via USB (this is to install necessary drivers ; see more on this method @ http://www.hovatek.com/forum/thread-317.html )
3. Install Vroot on the PC
4. Launch Vroot
5. Connect the phone to PC via USB cord
6. Wait for Vroot to detect the phone
7. Click the Root button to begin the rooting process
8. The phone will be rebooted once rooting is complete
9. Done
How to root MTN Smart (Sm@rt) Mini S730
Procedure
1. Download Kingroot
2. Install the app on the phone
3. Ensure you have an internet connection on the phone then launch the app
4. Wait for all checks to be complete
5. Click the center button (with Root and some Chinese texts inscribed on it) to begin rooting
6. Wait for rooting to complete
7. You should see a green tick to confirm that rooting was successful