Well.. its hard to say, if you made any mistake on setup over a2b.
I would suggest to test his product with his all default option coming with his package. [there are lot of options, dont go thorugh all, most of option that most of us, we want first], So if you are success , then start to paly and change the option to your own.
Remember:- there are one "General setup" and another "agi-conf1" setup [you can make several "agi-conf2, agi-conf3 & so on.." setup for different tricks] in a2billing.conf. [If you are primary, dont make several agi-conf parameter]. becareful to set both setup ["General setup" & "agi-conf1" ] rightly [otherwise you will swim in river, it will be hard to find out your problem].
Keep the base currency USD in a2billing.conf under both setup ["General setup" & "agi-conf1" ]. it will be easier for you to go thorugh with others.
Write here, what is your Target or planning to do with this product, then I can tell you what is the minimum setup to do for your purpose