Currently, Atlas only supports the use of VietJet (VJ) credit shells.
For VJ credit shells:
You can submit a Service Request via EVA and describe your credit shell usage request. Atlas will assign a dedicated staff to assist you with the process.
Path: ATRIP → Bookings → My Bookings → Booking Details → EVA → Ticketing Enquiries → Issue Tickets → Issue New Ticket with Coupon → Raise A Request
For other airlines, please contact the respective airlines directly for assistance with credit shell usage.