Hi,
I might be able to lend a hand. I am using an old Alcatel Speedtouch USB modem from the UK also, which I also struggle to setup. It is not the same model as the one in the eBay post, but you might have more luck with this approach (possibly).
Mine also reads ISDN, that is not a problem, and mine works at full speed. The problem was that you couldn't edit the settings from the software, you had to edit a file before installing.
Here is what I did:
First, uninstall all the software for the modem and for PPPOE that came from Telkom.
Second, copy the installation files for the modem to your hard-drive somewhere.
Third, locate the phonebook.ini file and modify it to look like this:
[Version]
FileVersion=1.2
[Driver]
DriverType=1
[Maximum simultaneous connections]
MaxSimConnections=1
[0001]
FCS=2
Name=ISP number 1
VpiVci_VCI=35
VpiVci_VPI=8
EncapsulationMode=1
PeakUpStreamBitRate=8
PeakDownStreamBitRate=16
Next, re-run the installation using the modified phonebook.ini file.
Last, re-install the PPPOE software that comes from Telkom (Polyglott or something).
You may have to fiddle around with modifying the phonebook.ini file depending on the version of the drivers you are installing, or if it has one at all. However the [0001] section has the necessary settings.
There was another post about this a couple of years ago. I will try to find it and post a link here. The explanation there may be better than mine....
Good Luck.
[EDIT]
I struggled with newer and older versions of the drivers for this modem. Only 1.2 seemed to work (after lots of trial and error). If you need a copy of that version of the software PM me. However, I am not sure that these drivers will work with your modem as it is a different model.
[/EDIT]