When dealing with buyers on the internet, you are always susceptible to fraud. At any given time, someone can open a claim for unauthorized activity, or anything else just to get their money back. Point is...you've got to be careful about your business and do everything you can to keep yourself covered.
Why do not you ask them directly - 2CO will only activate your account after they review the contents of your website thoroughly. You just cannot put a 2CO subscription or payment button and start selling like Paypal!
So, 2CO call every customer ? If yes, then how fast after customer placed the order ? What if customer phone is on AM for the next 4-5 days ?