We absolutely believe that notification should be mandatory. It would be nice if they would also explain to these people why they're changing their credit cards. No one has been told why; it has just been, here you go, you're getting a new card. And of course this raises all kinds of suspicion in people's minds, which is part of the reason we're getting the phone calls.
Speaking personally, two years ago the Bank of Montreal did the same thing to me. They phoned and told me they were sending me a new card, and not to use the one I had. When I asked why, they said they couldn't tell me. Even when I said again that I wanted to know, they said they couldn't tell me.