[Resuelto] Switching from pay-as-you-go to prepaid

Background of the issue:
I am trying to switch my site from using pay-as-you-go to prepaid credits. I have already purchased 50 Euros of credits.

Symptoms:
The instructions mention a 'Stop using pay-as-you-go' link, which I cannot find on my page.

Questions:
How can I switch my site from pay-as-you-go to prepaid credits?
Why is the 'Stop using pay-as-you-go' link not visible on my page?