If an insurance broker sells you an insurance "program" but will not tell you who the underwriter is, how can you find out?
Question Details: Is the insurance broker required to tell you who the underwriter is? If not, how can you even know that there is a policy behind the program?
You can't force the broker to reveal this information, other than by filing a legal action against him or her (such as for fraud, if you suspect such; or breach of contract) and using the legal mechanisms of litigation (such as "discovery"--e.g., written questions which must be answered) to obain such information.
If you haven't bought the progam yet, don't: as a good rule of thumb--and I'm a former SEC attorney, so I know whereof I speak--never buy any financial product from anyone who will not disclose full information about it to you.