There are 3 parts to this wonderful equation:
1. Telkom telephone line connected to a POTS point at the exchange, you connect a phone to this and make calls and Telkom charges you for those calls, you pay Telkom for this part.
2. Telkom ADSL line connected to a DSLAM port at the exchange, you pay Telkom or a provider of your choice for this part.
3. Login and Password from an ISP who deals in ADSL to provide you with access to the internet, you pay the ISP for this part.
Part 3 requires part 2.
If you cancel part 2, then part 3 will not work, and you'll still have part 1.