Allegiant Airlines Customer Service Phone Numbers: +1-877-552-0621 or (702) 505-8888 To connect with Allegiant Airlines' customer service team, you can use their dedicated phone numbers at +1-877-552-0621 or (702) 505-8888. These lines are available 24/7, ensuring that you can reach a knowledgeable representative whenever you need assistance. Whether you're seeking guidance on changing a passenger name, have questions about your flight, or require support with any other aspect of your travel plans, Allegiant's customer service team is ready to provide expert assistance.