My site accepts credit cards through PayPal, but some customers still send me credit card information in their e-mails or purchase orders. PayPal does not allow me to use this information to charge their credit cards.
Is there a service that has a low setup cost and effort that I can use to charge customer's credit cards if they send me the info over mail or over the phone?
PayPal allows you to enter these details manually using their 'virtual terminal', this 'feature' costs an extra £10 per month though. - But given you are using PayPal already, this is certainly the easiest way.
With a little help from my friends, I found out that Ogone provides a service like this (Virtual Terminal), also to European customers: http://www.ogone.be/en/solutions/payment_processing/Call%20Center.aspx However, the legal implications in Europe are different from what they are in the US. Basically, if you're not shipping a physical item and you are charging your customer's credit card on a virtual terminal, you as a vendor might get into trouble sooner or later.