1. If it's not an interest bearing account, there is nothing to report on a 1042S and no need for any certification of any type.
2. If the W8-BEN is current, reporting is required for most countries, but withholding is not.
3. Not enough information is offered to answer the question, but you need to make certain that this is the appropriate form for your customer; i.e. it is not a U.S. entity. Consider whether your bank should be offering interest bearing accounts to foreign entities if it does not understand how to handle their income tax ramifications.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.