Short answer: of course you can! Anything can be a bayonets, the differentiation comes from the entrepreneur in securing that market. You have, in a microlevel, proved that there is a need and is just a matter of how big that market can be.
What I would do, if in your shoes is keep the idea simple. Target only one industry or type of phone call in which there is in fact a benefit of having a third party listening to a call to then offer suggestions. The phone calls that you guys made could be the type of call to focus on! But it has to be one where the feedback is the only service to the customer.
Don't get too hung up at first about monetizing, once you find the right type of call you can then focus on how to monetize. You can charge businesses within that industry or charge customers directly.
If you charge customers directly maybe have a prepayment processed similar to clarity for example.

If you need more feedback give me or another a call
Best of luck!