Originally Posted by BillyHoe

I don't use regional billing. I found it hurt my sales alot. I still find the odd site CCBill messed up on but you can hard-code the USD (or whatever currency you want) in your join page, to avoid it.
For your security issue have you host only allow CCBill's IP to access the script and you should be fine.
Hit me up on ICQ if you want and you can share your suspicions. I have a few suspicions to why sales jump up and down sometimes as-well.