Prepaid Calling Card- Setup and Documentations

I need someone who can set up and configure calling card solutions on my test server which includes Centos, Asterisk , A2Billing along with the other requirements to set up the calling card with the astersik and A2Billng configuration. Person who can also show us and provide documentation in terms of configuration and setup. Please note: This is just a trail setup and we not not making this live currently. After the trial set up then I require some one to officially setup the same and can manage remotely and provide on going assistance as and when required with the asterisk and A2Billing support. A person needs to provide the cheapest SIP providers as well. A person with the extreme knowledge are allowed to bid only.