Basic Economy tickets cannot be changed, but can be canceled subject to Avelo's cancellation fee.
Avelo Airlines Chane Flight Policy says Passengers holding Avelo refundable tickets and want to change for free will not be charged a change fee.
Changes to Avelo's refundable tickets are free and there are no change fees.
No-Risk Flight Change or Cancellation Period - If the passenger cancels the ticket within 24 hours of booking the ticket, regardless of the ticket type, the flight change is free of charge.
https://www.cancelation-policy.com/blog/avelo-airlines-flight-change-policy