Ask them to trace it. Not the general answer about how they handle data, the specific answer about the specific list they're about to dial. If the answer is vague, the risk sits with you, not them.
Inside the first ten seconds, unprompted, on every call. Anything later is a decision to see whether the person notices first.
Make them demo that exact call, live, on the spot. Not the good call. That one. The response should be immediate, unconditional, permanent, and applied across every channel they run for you.
The lead's, not yours. If a vendor has to think about that answer, they built it in one time zone and never tested it in another.