Extreme Signal Problems

I stay in North West and work in the Pretoria region. At my house i have to manually change my signal to roam on Vodacom. Once start driving the signal has to be changed manually back to cell c signal. As soon as I drive out of Pretoria the signal must be changed manually back to Vodacom again. My work colleges and customers are struggling to get hold of me. So much so that I have been called into a hearing for not having my phone on. How should i know when to switch to Vodacom and when to switch to cell c? Is it my responsibility to make sure that I have signal or should cell c have this covered?

The answer is obvious: I pay and they must deliver what they promise. I do not want a walkie talkie that constantly need a channel change!!!!!!!!!!!!!!!!!