Do you have 24 hours to cancel with Frontier?

Yes Frontier Airlines does offer refunds by phone at FRONTIER but the eligibility and conditions vary depending on several factors including fare type route and the reason for cancellation. Passengers may be entitled to a refund if they cancel their booking within the allowed timeframe and meet the criteria outlined in Frontier Airlines

Source: https://community.expensify.com/discussion/13927/do-you-have-24-hours-to-cancel-with-frontier-help-for-customers/p1?new=1