Frontier Airlines Flight Change Fiasco - Atlanta to Cancun

We had planned a trip from Atlanta to Cancun, Mexico on June 24, 2023. We purchased round-trip Frontier Airlines tickets via a travel agent.
Our outgoing aircraft, F9 153, was planned for 02:45 pm from Atlanta, GA (ATL) to 04:29 pm Cancun, Mexico (CUN), with a direct flight time of 2 hours and 44 minutes.
When we arrived at the check-in website, we realized that our flight had been changed for 06:05 a.m. with a layover in Chicago, resulting in a 10-hour journey.
However, neither the airline nor we were notified by email or SMS of the change in flight time and layover. We tried calling, but no one responded. We phoned our travel agent to cancel our flights and purchased new Delta Airlines tickets for five individuals for a direct round-trip to Atlanta. Because we booked the tickets on the last day, we had to pay a high price, which made us even more inconvenienced.
Our travel agent was able to contact Frontier Airlines solely by email, and after a lengthy wait, they processed the refund for the tickets with a hefty deduction, long after the event occurred.
We do not want others to suffer in the same way that we have. If you order tickets with Frontier Airlines for foreign travel, they may reschedule your itinerary without warning, turning a 3-hour flight into a 10-hour one with layovers, and leaving you stranded at the airport with no one to speak with. They can ruin all of your trip arrangements, take no responsibility for it, and only refund you after sending many emails and deducting considerable amounts.