@cardine -
There are several ISP's that will take "ownership" of your ADSL lines for you.
Usually, there are 2 reasons for doing this:
1 - Usually, the ISP ADSL line-rental is a tiny bit cheaper than telkom. Like R13 or so.
2 - If you have problems with the ADSL line, you can call your ISP instead of calling telkom, and you are under the impression that your ISP will provide better service than telkom.
But, you still have to pay telkom for the telehpone line rental, and, if the line stops working (voice calls), you will have to call telkom anyways, and, now you'll have 2 bills to monitor.
Then, you mentioned Telkom Gig's.
There is a distinction between telkom the ISP and telkom the ADSL Line provider. They're 2 seperate things.
You can at any time switch to another ISP without signing your line over to them. You call telkom the ISP on 10215, and cancell your ISP deal with them, be very careful and clear and tell them that you are NOT CANCELLING THE LINE, just the ISP part. They will tell you when the cancellation will take effect.
Then call your preferred ISP and buy bandwidth from them, but only once you are sure the telkom ISP bandwidth is cancelled.