Lourens,
You might find this surprising, but you'll probably be doing best just getting the TelkomInternet offering.
All the other ISPs offering internet over ADSL service simply resell the service provided by Telkom, usually at a higher rate, but sometimes, they throw in some value added stuff, like hosting, extra e-mail accounts or the ability to buy more bandwidth. Depends what you need who will be best for you.
If you are a very conservative user and doubt that you'll ever need more than 3GB of bandwidth a month, go for TelkomInternet. To be very honest, everyone sucks just as badly. At least, with Telkom, you don't pay much for the horrific service. Also, as one small consolation, Telkom include the bill on your phone bill, so you don't have to make extra debit order or other arrangements to pay it.
TelkomInternet charge a maximum of R249 per month for their basic internet over ADSL option. I say maximum rate because the fee seems to be calculated on a per-day basis, in shorter months, the amount on the bill will vary from R230 to R245. Other ISPs will charge a fixed amount anywhere between R250 and R300. In some extreme cases, they might even go up to R500 (Hello M-Web!), but usually throw in value added services at that point.
In my humble opinion, if you are paying more than R250 per month for the standard 3GB capped offerings, you are getting ripped off badly.
There is one exception to the statement above. If you are looking to spend some real money, there is one ISP that isn't just a reseller and that will offer you superior service to TelkomInternet and all the other reseller ISPs.
If you have at least R1200 per month to drop on ISP fees, you can go for DataPro. They offer internet over ADSL service mostly targeted at business which includes a managed UNIX server set up at your premises to handle your mail, act as a proxy and provide group calendar support, etc, for businesses. The real feature of DataPro's internet over ADSL offering is that it has no bandwidth limit. In other words, you can download as much and as often as you like. No post-3GB end to international surfing.
The DataPro option is costly though, so unless you are very serious about internet access, don't go there. The R1200 per month is just the ISP fee, this does not include line rental, which you are already paying. So, if you have the business ADSL line from Telkom plus the business internet over ADSL offering from DataPro, you can expect to pay about R2000 per month for internet access.
If you have R2000 per month to spend though, it's well worth it.
Willie Viljoen
Web Developer
Adaptive Web Development