Paying for a data-sim card with no signal for 4 months. And still not fixed

Have an upgrade 4 months ago. Since the upgrade the sim card has stoped working. We have contacted vodacom about the problem…. No luck. Complained via the fb messenger still no luck. So we are paying R300 per month for nothing a sim that has no signal at all. They promise and promise someone will call but no call. Every time they tell us. Switch off the router rest it put in another device……. We have do e it over and over and over. That is not the problem, they just dollnt want to understand it. All the other sims we put in the same devices are working 100%.