****** by MTN

I have a contract with MTN that charge me R249 per month. Before they send me a router they wanted me to pay a pro rata and I paid it and they send me the router. They deducted another money but after their router was not working for the whole June and July, but I kept on paying every amount due. I called them several times without help but promises that is going to work but nothing. I want to know what else must I do.