Have you ever stayed (or booked) there before? If the hotel already has your Bonvoy details, then they might have been mistakenly applied to somebody else sharing your name. It's far less likely that somebody hacked your account and booked a stay using your payment details - the named guest trick wouldn't work in Vietnam.

But calling Bonvoy to have the stay removed from your account wouldn't do anything at all to ensure that the points and stay credit find their way to the actual guest. I wouldn't feel bad about doing nothing and accepting the "gift"