As far as I can ascertain, the standard telephone cables available here are mostly flat (not the proper "twisted pair" required for ADSL). If you use ordinary cable to connect your router/modem to the phone line, you will most likely lower the speed of data transmission. The longer the cable and the faster your available speed, the more it will be reduced.
As an example, a 3 metre "twisted pair" cable increased download speed from 6.87 to 7.02 Mbps. It's not a huge increase but I know that some people like every bit of speed they can get to prevent the dreaded "buffering, please wait" message!
The special cables can be ordered direct from my SatCure web site but the postage cost is ridiculous. However, if enough people are interested, I can put in a bulk order, which will be much cheaper.