Billed for their mistakes

I have been billed +- R3000 for a charge that is there fault, I dont have R3000 to pay them. I have tried going into their shop, I have tried phoning, when I do phone, they are always on strike, computers are down. I tell the same story over and over again. The Accounts department is supposed to get back to you within 3-4 days, I am still waiting since this last time the 21st august. They told me I must tell them what the problem is give them dates, they are the ones that have record and phone recordings of everything, now I must pay for their mistakes and do their job for them..... I have had endless problems with mtn and no one can help you. They make my phone bill whatever they like. People hack our lines, their own people and we pay for it. I tried to phone now again to sort this out, it says my no. Is invalid, how do you sort out a problem when you can never get through? Maybe they should spend less on advertising and more on customer relations! I want my contract cancelled, please help. All we do is pay for their mistakes, they are taking advantage of us and know we are bound by a contract that doesn't protect us from them. Kind Regards Lisa