There are many options that you can go with, but if keeping the land line us a requirement, I would suggest you stay with ADSL or perhaps a fiber option if Openserve is in your area.
To get ADSL, just browse to the Afrihost site, and select one of the adsl bundle options, either capped or uncapped. During the sign up it will ask you for your land line number. Afrihost will then handle all dealings with Telkom to get your ADSL provisioned, including the billing for the adsl portion at the speed that you have chosen. Once everything is set up, if you chose a router as part of the package, Afrihost will send you a router, and instructions to set up.
Fiber is almost the same process as the above, except during the process you'd need to be available for someone from Openserve to come through and do the fiber installation.
I prefer fiber due to the low latency and higher upload speeds. But that is a personal preference.
Afrihost have made it really easy to do. But If you'd prefer to go the long way, you can can always contact Telkom to get ADSL provisioned on your line, then verify the line, then get a router at your own cost, and set up the Internet yourself. Telkom will try and sucker you into one of their packages, which sounds enticing, but Afrihost is the way to go, if the awesome network doesn't wow you, the ease of use of the client zone will, not forgetting the awesome support.. (Remember they handle Telkom, and in personal experience, their SLAs with Telkom mean your line gets serviced weeks before you would even hear back from Telkom themselves)