The top up will be charged to the account details give to Afrihost on sign up.
The same account that is debited monthly for services from Afrihost.
This can be managed in your Client Zone - https://clientzone.afrihost.com
If you require further assistance please email: email@example.com
or contact Afrihost support on 011 612-7200
or see our FAQ page: http://faq.afrihost.com