best PCRF for pre-paid mobile solutions?

I am researching some PCRF solutions for some work I am doing with non-US operators, and I am looking for features that work well in pre-paid mobile environments, particularly ones that want to cap or charge 3G and WiFi at different rates / levels. Any suggestions or contacts? -- Also on LinkedIn?  Feel free to connect if you too are an open networker: scubacuda@gmail.com