Are such databases being sold somewhere? I couldn't find them on the marketplace. Maybe it's possible to parse mobile phone numbers from social media sites? There is no guarantee that those people would have a Viber account, of course, but it would still be better than just going over a range of potential phone numbers. Can phone numbers be parsed from Facebook for a certain group of people, for example? Or any other social media site? I would be glad to hear any advice on this topic.