Gingerbread was released months ago. Install kies on your pc, and check that you have the latest version of kies.
Then plug your fone in, and you should immediately get a popup notification telling you that there is new firmware available.
I do know of some people on MTN simply being unable to update their firmware, because kies keeps telling them that they are already on the latest version. In that case, simply take it to your nearest Samtech or MTN store and ask them to update if for you.
There's also the unofficial way of updating your firmware, which voids your warranty however, and can (but very very unlikely) brick your device. I'm assuming that your device is still new and you are probably not too keen to do anything like this.