And when you receive the voicemail, did it indicate where it came from ??? i mean the telephone line provider surely can find out for you right ??
Sorry, didn't the OP say the message, when played forward, gave her six messages, then she played it backwards and got 'we love you'... clever 'ghosts' to know how to say stuff forwards which also gave a backwards message, eh?
Telephone line providers can't provide the caller ID if they chose to withold it, or if it came from a 'call centre' or if it was from overseas. If they are asked to, they can provide future caller ID's but it's difficult to do it after the event, and would cost money and you would have to have a valid enough reason to request such info, that's why we have the option to withold our numbers, for privacy.
Come on, OP, post the message forward for us to hear in its entirity, we're intrigued.