Do you have a seperate BIN for business cards? If not, I would check with VISA or MasterCard as your BIN may be licensed for consumer cards only.
We set up a Business Visa Check Card product a couple of years ago. The good news is that Reg E doesn't apply,the bad news is that Visa extends zero liability to business cards. I think the answers to your questions lie in the provisions in your card agreement with the business.
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Let's start at the very beginning; A very good place to start...