pay for a service we dont receive

We recently had an uncapped 4mb adsl line rental with wifi router installed at our house for the amount of about R779 per month, since that date of installation till now we arent even running speeds of 1mb! Have called the call centres to lodge complaints as well as the initial installation guy did so too just last week when he yet again came to check on the line and downloading speeds. Apparently the problems lay between our house and the telkom box on the next corner, including underground cables. Now we are in a new month, payment is made and we are still sitting with a ****py internet connection. What are we paying for? And what is going to happen about this mess? For how long do we pay for a service not being delivered to us?