If you wish to remove/disconnect your PayPal account from your Challengermode account, you can do so in your PayPal account under your "pre-approved payments".
To view or change your pre-approved payments, 1) login to your PayPal account, 2) Navigate to the Payments tab:
3) and click on "Manage pre-approved payments". This will take you to a list of all the shops, site or merchants you have a billing agreements with. Look for the one that says "Challengermode AB".
Please note that you can only have one PayPal account connected to your Challengermode account for security reasons.