Home internet

We took out home internet with MTN,they told us that we must pay on the 15th of every month for the internet to stay on we did so and even on payday they twisted their words to make their sale probably yet the wifi always only went on the 1st of every month and goes off the 15th of every month which means a person pays all that Rands for 15 days of internet!!! It's a ****, then when we tried to cancel the subscription they say we must pay the previous months payments including the current when we have been trying to cancel it because we don't want the internet anymore they are *****ing alot of people and I find it unfair, how can you pay a subscription you don't want to use in order to cancel it and there response is that's how their systems work its ridiculous honestly!!.