Restart router once a week, just to be sure, most newer routers will do a refresh periodically as far as I know.
If you're on a normal ADSL connection, check your phone to see if there is static, if there is, I'd advise replacing the adsl filter (especially if you've had a thunder storm recently).
Also do speedtests and a simple ping to a server (google.com or whatever you choose) - Windows key + R - cmd - ping www.google.com
Check for packet loss, it will send 4 packets and you should get all 4 back, if not, you're losing data somewhere.
Call Afrihost, more than likely they'll know what to do and help you accordingly.