Worse network provider

I took a contract with them for 20GB each month, yesterday my data got depleted of which I both R200 so I can buy DATA only to find out that they took R140 from that amount, when I sent them an email asking why they deducted that amount I was took that I had subscribition, I don't remember subscribing to anything...bare in mind that the sim it's in a router on a cellphone so how could I have subscribed to anything. I want my R140 Back.. MTN is the worse network ever.... The number for that contract is ***