Call accounting for Quintum’s VoIP netwo

Hello,
I’m running an international VoIP network based on Quintum’s Tenor Gateways and would like to add a call accounting system for my network.
Can enyone advise or recommend for an accounting system which is intergrades with Quintum’s GW ?

I’m not talking about Billing solution or calling card.
My neywork is only for an internal use. It’s a VPN network between my offices.

Thanks
Shannon.