Unfair practices

I took a 3 year contract with netstar. Lost my job for over a year. I then arranged to pay my contract off as there was still about R4100 owing. Arrangement was excepted. I still got calls telling me the account was outstanding, sometimes up to 3 a month regardless of our arrangement. I eventually asked for a statement. I was shocked and horrified to find that not only dont they put my payments on my account but also charged me R529 for telephone calls! After a year of payments I owe more than what I started off with. This is the most unfair practice i have seen in my life. It is like kicking a dog that is down already!