This might be an easy thing to fix, or point to a problem.
The easy thing is to make sure that you have data, and have not been capped.
When you get capped, you normally can still access the Afrihost website, in order to top up your data.
You could also switch off your modem for 10minutes, and then switch it back on. Make sure you also remove the power from the modem. Some modems are not very stable if they run for a long time. This should also be done if your ADSL port had been reset.
If this is not the cause, then you should send, via different connection, information like trace route and ping outputs to the Afrihost support team.
This might assist them to resolve the issue.