From what I understand, if the issue with only incoming configuration then it shouldn't cost you more that $15.
Relevant Skills and Experience
I have been working and managing FreePBX, GoAutodial and Vicidial since last 4.5 years.
Proposed Milestones
$20 USD - Check if inbound calls hit the server through asterisk and then route it to proper destination.
Additional Services Offered
$2 USD - check the security and firewall
Just to be clear and specific, You want to configure the inbound calls right?