ESH.
In my family business, rule #1 for reception is "unless you're dealing with a client, stop what you are doing to answer the phone". Every VM is responded to ASAP and the box is cleared at the end of every day.
WM answers their phone, this likely doesn't happen. OP starts a thread more like, "hey, just want to check in, haven't gotten a shipping notice yet" and this doesn't happen.
Regardless, you don't publicly state a customer's card was declined. Charges are declined for lots of reasons, not just NSF.
Stating the card was declined is fine as they never stated the reason why.