Purchase your Allegiant Air plane ticket at the airport desk:

https://www.tackleunderground.com/community/topic/89784-how-to-contact-delta-airlines-for-an-online-reservation-da/

Here you can get to know about how you can do Allegiant Airlines flight reservations through airport:

✅ Visit the Airport: 

If you’re flying Allegiant, you should visit their desk at your departure airport.

✅ Speak with a Representative: 

Go to the desk and tell the customer care person you want to book a flight.