They gave wrong dates and we didnt get back our money

We bought ticket via online but they issued our electronic ticket with wrong dates, We immediately tried called the hot line - no answer. We wrote email they answered next day that we must call the hot line. We called again, No answer. We had to go to the airport to get in touch and ask for help to give us ticket with the right dates. They said they can change but it will cost for us. Wich is unacceptable as the wrong date was issued by TURKISH AIRLINE's system. After many argument they recommended that better if we cancel them and rebook. After cancelation they said this tickets are not refundable. After many letter they gave us back peanuts money. They say they dont have refund policy. Which is not true. I can cancel my ticket in 24 hours - we did so - and the most important that THEY GIVE US WRONG DATE! THEY MADE THE MISTAKE.