Misrepresentation at time of sale

When I enquired and subsequently app**** for a landline and ADSL line installation, I was instructed to pay a R700 deposit before the installation could take place. I asked the sales person at the call center what it was for but she could not explain it to me. I then asked whether this deposit would be offset against my first bill and she said that it would be. I then paid the deposit and my line was installed. I received my first bill recently and noticed that the R700 is merely a footnote on the bill and does not offset anything. I called the call center to enquire and they informed me that the deposit is kept by Telkom until such time I cancel my line and then it is paid back. I requested more detailed info around the deposit (terms and conditions) but the agent said she was informed by her supervisor that she cannot divulge this information and that all customers are required to pay the deposit (I have since found out this is an outright LIE). I either want my R700 deposit to offset costs on my bill or I want it paid back to me and all costs incurred by Telkom thus far for my account written off and my account closed as you misrepresented your products and services to me.