Unacceptable service

We bought a itel cell phone and within 4 months a had problems and they replace it with a new phone, now this phone is also giving problem's and sent for repairs. We have been waiting 5 weeks now and every time we query we are told they don't know or it's still being assessed and the same when querying at Vodacom, this is unacceptable and my wife requires a phone as it is part of her business operations