There isn't a way that you can only be charged for CC Payments, once you upgrade, they charge for every payment afterwards regardless. This really annoyed me too, especially since when I was using it, I had a lot of $15-20 payments, and the only people I accepted CC payments from were Europeans, since at the time, they couldn't pay me any other way.
However, it is possible to downgrade your Paypal account to regular, and I have done it before. I don't remember the exact process, but the easiest thing to do is to go to Paypal's help section, and search for "downgrade", and it will tell you how to do so.
You can only do this once however, so if wish to have a business account again (ie, accept CC payments), and upgrade, you cannot downgrade again. The entire process should take about 2-3 days, and Paypal will email you asking to confirm that you wish to downgrade during this.