Bad service from MTN South Africa

It's now been more than a month since I started complaining about my uncapped wifi from MTN. I've been phoning then 2 or 3 time a week. They keep saying the tower is faulty and the technicians are working on it but every day its running on less then 1mb/s. Its supposed to be 10mb/s. Can someone please help me or must i seek legal advice.