You can do this with the business level uncapped account. BUT
Afrihost won't be able to set this up for you. You'll have to get a Network Administrator who'll do this for you. Please make sure you use the Zyxel SBG3300-N from Afrihost or a better version coz i know they support this one. You can do this with this device.
I'm assuming this is what you want to do from the diagram.