Unacceptable lack of service

Huawei Modem - modem kept on switching itself on and off constantly. Struggled for two weeks, were then told to send in for repairs. Got a message the replacement will be done within 2-3 days. It is currently 7 days and not yet replaced. When I call they just say they are out of stock to replace so I must wait. In the mean time my business relies on internet and I am loosing money daily. If they do not have the same in stock surely not my fault and they should at least replace with either same or better model. The Vodacom Care centre in Menlyn's phone lines permanently has issues with it being down, being cut off and I have probably spend hundreds of rands already just holding , having to call back several times and then holding forever then no news. This is unacceptable. 4 months before contract ends the sold device no longer works.