Spirit Airlines Paid for a ticket on flt.167 to Phoenix Az. 4/1/15 round trip, since they changed the gate I missed the flight and could not get on another and they would not refund me my ticket. Mirimar Florida

Since I did not have a ticket I arrived at the airport two hours early, checked in my suitcase and went to the indicated gate.  Since it was very crowded and I was so early I sat at another open area which was very noisey. As it got close to my flight time I went back to the gate and the flt was not on the board.  They also did not have any type of billboard showing flts coming and going times as other airlines do. So I finally asked someone at the desk and she exclaimed I was at the wrong gate and they made an announcement which I never heard.  I rushed over to that gate (the plane had not left but most people had boarded) and they told me I had to be there 15 minutes early and I told them I was there two hours early. They told me to go back to the main entrance to try to get on another flight.  I am sure they gave my seat to a standby.  I was never paged by my name which other airlines would have done. I thought I would try this airlines since the price was reasonable but I see now they over book.  I wrote a letter to their office and they never really answered me except by email saying it was my fault.  I do not have a smart phone and I was traveling alone or this would not have happened. Now I lost $300 between luggage checking in and transportation to and from airport and the ticket. I paid for insurance too and they saidd they do not cover these situation.  I am on social security  and I know I am not the only person that this has happened to.  They next day when I went to pick up my suitcase another lady was arguing with manager that the same thing happened to her and she was in tears. Now I do not want to travel by air ever again. Please help me find some justice here.  THank you, Shirley H