How to Contact United Airlines at London Heathrow Airport? Traveling with United Airlines at London Heathrow Airport? Know how to reach United Airlines at the airport for assistance. Call United Airline customer service at OTA: +1-800-971-7347 or USA: 1-800-864-8331. https://skyairbus.com/blog/how-to-contact-united-airlines-at-london-heathrow-airport/