Frontier Flight Change Policy-1-844-402-8105

The cost to change a flight under the Frontier Flight Change Policy varies. If a change is made 60 or more days before departure, it's typically free of charge. However, changes made closer to the departure date can incur fees. These fees escalate as the departure date approaches. Under the Frontier Flight Change Policy, it’s always cheaper to make changes sooner rather than later.
For specific inquiries about change fees and timings, you can contact Frontier at 1-844-402-8105 or 855-559-0155.

source: https://groups.google.com/g/comp.os.vms/c/PFyeoaYviP4