The fastest and easiest way to upgrade your Magpi account, or to purchase upload or message credits, is to pay with a credit card from your account page. Just log into Magpi.com and then click your username in the upper right corner of the screen:
This will bring you to your account page, with links to upgrade and purchase credits:
Once you have selected your plan or credits to purchase, you will be asked to enter your credit card payment information:
NOTE: Charges will show up on your credit card as Magpi.