Frontier has become almost impossible to deal with. I had a similar notification but the 9 hour schedule change was unworkable. I hit cancel which brought up a screen on cancellation options. I ticked the "refund" box. The only option was to then press the "accept changes" button below that. Not clear if that meant select changes to flight or select changes to the reservation by now cancelling it. So I went through the same loop 2 more times always coming back to the same place. So I went ahead and pressed the "accept changes" button" but it just confirmed the new flights. Decided to pursue it on the online chat bot but it was completely useless as well.

Bigger issue is that I have flown scores of flights on Frontier over the years, saved a bunch of money, and never had any major problems, but really starting to wonder if it's worth it. They change the schedule frequently, have no way to speak with anyone to solve problems, very poor IT, and then the airport and inflight experience has become really unpleasant with the harsh and aggressive rules enforcement during boarding and once on the plane. Then there's the tip request when you buy a cup of coffee on board. The entire experience is just not worth it any more.