No matter which DSL package you are using or provider that you are paying for access, you will always receive a dynamic IP assigned to you. Telkom makes it impossible for any ISP to assign a static ip on that level, hence why all ISPs are using tunnels.
Once you have authenticated your dsl account and received a dynamic ip, you initiate a tunnel to a LNS on Afrihost's network, in order to authenticate and assign a static IP. Of course, the customer's modem/router needs to be set up correctly so that it now route all traffic over the tunnel and not the dyanmic ip.
If your network engineers setup the LNS correctly, they would only allow certain IPs to be able to authenticate the tunnel in order to receive a static IP. There should be no reason why you can not add your own mobile 'dynamic ip ranges' to the LNS so that the tunnel can be built over either DSL or GSM.
Thats now if you have your own ip address space on your APN and not using MTN's space.
Michael
I'm not sure if that is the way that our system works, though what you describe sounds more like bonded tunneling, which also sometimes requires static IP addresses
To my knowledge, when you authenticate on our our network, we assign you the same IP address for every session, and that is controlled by our & MTN's radius servers. I don't believe that Telkom is involved at all but let me check it out so I can answer more thoroughly