Yes — you can cancel a flight with Frontier Airlines but the terms depend on when you cancel and what fare you purchased:
If you cancel within 24 hours of booking and your flight is more than 7 days away, you’re eligible for a full refund.
After 24 hours, for most fares you’ll lose the refundable cash value — you’ll instead get a travel credit, often after a $99 cancellation fee for basic/standard fares.
Some fare bundles (Economy, Premium, Business) waive the cancellation fee.
If you tell me the fare type you booked, I can check the exact fee for you.