While preparing for a trip to London, I downloaded a local app for walking routes and guides that required a British contact number. The system rejected my Ukrainian number, so I visited a webpage listing free UK numbers (https://onlinesim.io/free_numbers/united_kingdom). I selected an option with the +44 code, entered it into the app, and immediately spotted the required four-digit code in the feed. The app launched, and I gained access to an interactive city map even before my flight.