The number on some says 'INTERNATIONAL', but if a number is displayed, it is often fake, using a dialling code that doesn't exist.
Lately I have been getting many calls saying I have ordered an i-pad or similar from Amazon or ebay for a several hundred pounds, which will be taken out of my bank account - I am to 'press 1' if I didn't place the order. They all go to the answering machine. I only answer if I know who is calling.