I’m very sorry to hear about your dog! @cbwahlstrom is no doubt correct that there isn’t currently a voicemail box currently associated with your old Republic number. That said, it’s unlikely that number has been assigned to another customer at this point. Please consider opening a support ticket when signed into your Republic account here: Republic Help.
Perhaps, the number might be temporarily restored to your phone, so someone using it to reach you about your dog could do so? I do not know whether this is possible or what complications it might create with your new number but if it were my dog, I’d be willing to take most any shot potentially available to me. If you open that ticket, please let us know the ticket number and I’ll ask staff to do what it can to expedite.