Every flight we’ve booked with Frontier has had the flight time changed. One changed early enough that we now have to pay for a hotel the night before and maybe the night we come back. I did receive an email each time and was given a chance to cancel the ticket if the time was no longer convenient. The flights that only changed a few minutes, I was not given an option to cancel. Maybe call them and see if you are signed up for emails or make sure it didn’t go in your trash/spam folder.