If you are traveling from United Airlines and want to choose a seat in United Airlines then by dialing this customer service no:(1-800-864-8331) you will be connected to a United Airlines representative. You must choose your seat within 24 hours before flight departure and avoid paying any unnecessary charges. Further, selecting a seat is always reasonable ask you to United Airlines seat selection fee is around $10 for short-haul flights and $50 for long-haul flight journeys.