I pay a lot of money for nothing

I had 4 telephone numbers on my account, for me and my 3 children. When one got a job she got her own cellphone. When I could upgrade I requested that the her number be terminated. The Mtn staff member gave me a number to phone but I could not get through, so I went back and asked assistance. They terminated the number for me. I found out four months later that I am still paying R100 per month. The account was not updated. I can not change the contract now, I have to pay R100 per month for 24 months. For absolutely nothing. I have also found that sometimes R7 per day go off my cellphone account when I open a text from some third party. Surely the consumer law should protect me against that practice? But I'm sure Mtn knows well that I have no choice but to pay it from my meager salary, as I could not afford to take Mtn to court, and it would not help to change service providers, as the other cellphone companies will be as bad.