I have stuck to the same brand of phone for a long time, but I would move to samsung in a jiffy just to have the convenience of having all my cards on my phone. Less to carry. Hassle free lifestyle.
I don't have any issues with MTN at the moment. My only issue lies with all mobile providers that their prices have become outrageous. Its not worth upgrading as you pay more for less data, and voice. Also why carry on offering free sms's when the majority of chat takes place on whatsapp