OpenSER (Kamailio) + Asterisk + A2Billing on Amazon EC2

I have an a2billing + asterisk 1.8 Running on Amazon EC2 But i have issues with nat clients so i'm thinking to use Kamailio to solve nat issues and also get a more scalable system. I can give you Teamviewer access. I need the following: We need a serious professional to install and configure Kamailio integration with our Asterisk + A2Billing platform. - Kamailio should act as Registrar with Nathelper + RTPProxy/MediaProxy and it should allow local users to call each other without passing through Asterisk. It should also route local, national and international calls like to Asterisk + A2Billing so i can still bill them. - Kamailio should authenticate users using the Asterisk/A2Billing database - Asterisk + A2Billing should be configured so that new user accounts would be created in A2Billing. Also, each user should have their own voicemail account and Kamailio should route unanswered/failed calls to the user's voicemail. - Wholesale inbound calls should be authenticated by IP address. AMI 1 (Server 1) = It Has Asterisk 1.8 + A2billing (Already configured) AMI 2 (Server 2)= It Has Database (Already configured) AMI X (Server 3, or 1 or 2 if needed) = it Must have Kamailio (not configured) Flow: voip clientes ----->Kamailio---->asterisk+a2billing Since asterisk + a2billing are configuring and working, you wll only need to work with Kamailio integration. (You may also propose different server architecture design since we're working on Amazon EC2, migration is relatively easy for us) Note: We appreciate well detailed answer. If you have experience with Amazon EC2, Kamailio + asterisk/A2Billing don't doubt to bid. Regards,