What was the reason for your chargeback? Was it a stolen CC / paypal account? As I think that using some smart techniques you can smell out fraud, but there should be better methods.
One thing I've found is that people pulling fraud will sign up and first time do a MAX deposit that you allow. That's just a BIG RED FLAG. Why does someone sign up for say $100 when they've never used your service before.
At least that's how I think
It was a stolen CC. I think almost all banks give its customer 90 days to complain a transaction. Thats why!
For VoIP business it is still acceptable since the amount is not big (lets say 5 or 20 USD) but if you sell server, host (12 months charge) and other e-products, it hurts!
Paypal protect Buyer but is really lame for Seller. Moneybookers accepts VISA and other CC too, so I think it's worth a try.