VOIP Billing

http://www.voip-info.org/wiki/index.php?page=VOIP+Billing

Open Source Billing Systems

http://www.voip-info.org/wiki/view/Open+Source+Billing+Systems

Asterisk Billing

http://www.voip-info.org/wiki/view/Asterisk+billing

CDR Tool

http://www.voip-info.org/wiki/view/CDRTool

VOIP Billing System

http://www.webcdr.com

Billing VOIP Solution

http://www.sysmaster.com

VOIP Prepaid Billing

http://www.voip-news.com/sp/eye/ppbfb.htm

Nikotel VOIP Billing

http://www.nikotel.de/en/call-shop.htm

trabas VoIP Billing

http://www.trabas.com/opensource/TrabasVoIPBilling.html

Achieva Networks - Advanced VoIP Billing

http://www.achieva.com.sg/anvipb.htm

VoIP Billing Solution Vendors: List

http://www.iptelephony.org/GIP/vendors/billing

VoIP Billing Solution

http://www.webvoip.com

ISP VOIP Billing

http://ispbs.hostplus.net

VOIP-Pro Billing & Customer Management Software

http://www.inovaware.com/voip/voip.htm