Go to https://www.billing.qurextech.com/clientarea.php
>Enter your email address and password you used to register (refer to welcome email)
>On top bar click Billing
>Select my invoices
>click on the unpaid invoice that you want to pay
>on the invoice select the payment method you want to pay e.g lipa na mpesa or card payment
>Pay the amount invoiced
Then check in your email for the payment confirmation details and the transaction details.