Asterisk - OpenSER billing module required+

I now have Asterisk and OpenSER for a Voip + CaM, openwengo software solution. We are now getting PSTN and I require a billing module added and call forwarding, bestroute - and whatever elseI do not know about I need:) note: voicemail is prior installed. I looked at ASTBill, and would seem right, however I require some hand holding good advice and a helpful person. Please tell me what solution you would use and briefly why? RE: my budget you can place note in PMB explaining for your ideas what other cost should be...