A card is posted through your door from a company called PDS (Parcel Delivery Service) suggesting that they were unable to deliver a parcel and that you need to contact them on 0906 6611911 (a Premium rate number).
DO NOT call this number, as this is a mail scam originating from Belize .
If you call the number and you start to hear a recorded message you will already have been billed £315 for the phone call.
If you do receive a card with these details, then please contact Royal Mail Fraud on 020 7239 6655.

For more information, see the Crime Stoppers website:

http://www.crimestoppers-uk.org/crime-prevention/helping-prevent-crime/scams/postal-delivery-scam