Pretty much every ISP has troubles:
- Mweb with your issue
- Telkom with their throttling
- WA and their star rating
- Afrihost and their shaping
I don't remember any ISP's. So I'm ending there

But you get the drift.
Now in most cases, the solution is to upgrade to a business / premium account. I stand corrected here, but Mweb also throttles on their premium accounts. I don't know about Telkom. The star rating system still applies with their business accounts.
That leaves you with Afrihost business.
You get what you pay for, I know because I have a 2meg business account with them and I'm a heavy user. Besides being the best bang for buck / get what you pay for option, they're also the cheapest business accounts out there.
There are so many threads around here moaning about AH and how bad they are. So many people saying that they've been on the decline since MTN came on board. And in all cases (for the ADSL shaping issues in particular), they've been on a home uncapped account.
I'm quite sure that they are their business accounts are the best on offer.