Give telkom money to keep??? why?

So I app**** for an ADSL line from telkom. The person helping me told me that there will be no installation fees involved and I should get the line in about a week to two weeks time. To me this meant the first time I will be paying will be for my monthly instalments on my line. This morning I get an email from telkom telling me I need to pay a deposit of 700 rand for my line to be installed. A deposit for what you ask?? Well I dont have credit history and now Im expected to GIVE TELKOM MONEY TO KEEP in case I dont pay my monthly fees. Why would I apply for something I cant afford? As a matter of fact why would I pay money to them for a service thats not even guaranteed to work and I can only imagine how much effort its gonna be to get my money back from them. This is putrid.