Billing issues

Got my telephone bill with an extra line added with a 50% additional charge for my Adsl line which I did not approve. Went to gateway telkom and followed a queue for more than an hour and only to be told that they could not assist. They took down the query and my telephone number and said somebody will call. Who gives them the right to add charges to my account without my permission and why 50% to make something faster which is as normal as usual