OVERCHARGING CLIENTS.

I have a contract with Telkom for my wifi. In February they deducted R200.00 more, when I ask what is the issue, I was told that on the month of December they tried to deduct & there was no money. My contract says I pay on the last day of the month. Again today they deducted R200.00 more & today is the 30th. Whatever this people are doing, I am certain that lawsuit is the only thing that would alert them.