This is totally possible under a few circumstances. The first way I'd recommend doing this would be to have one modem and one line.
The modem has to support multiple PPPoE Sessions,which means you can set-up your Afrihost account on your PC if you only want one system to access
the account. Check out how to do this here http://www.tplink.com/be/article/?faqid=924
You need to keep in mind that both accounts will be sharing one line. And the line needs to be as fast as the fastest DSL Account. Otherwise,
you'll need to looking into getting another DSL Line installed on your premises, this would end up costing a bit more however.