Hi I was able to find it,
Sorry you felt I was rude, I don't think we sent a batch of whelks instead of Nassarius. I was able to find your order from 2017, and the replies we had. My reply to you was:
"Sorry to hear that, we do not carry whelks. I am familiar with the difference, we only have Nassarius in stock here."
I didn't mean that to be rude, I meant that to be factual. I thought you were asking, rather than claiming we sent the wrong species. Whelks cover a large number of species, in the hobby that it is usually a reference to any number of Buccinidae species. They live in areas different than where we collect Nassarius, it is very unlikely they could get in by accident, and more than one would have very low chances. They are not easy to collect in large numbers because these species prey on each other as well, and tend to be spread out. If you have a picture of the snails we sent still (probably not it was 4 years ago) I can ID it for you. I am confident we can correctly identify the snails we sell. You can usually tell a Buccindae species apart from a Nassarius by looking at the front of the snail, whelks have tapered siphonal canal, Nassarius are rounded and tear drop shaped.
I didn't see an email regarding pests in macroalgae in our email chain, but if you can find it I will look into it ASAP.