Pegasus Changed My Ankara-Stockholm Flight to the Wrong Route and No Response

I contacted Pegasus customer service to change my Ankara-Stockholm flight (October 4 - October 10) to Oslo-Ankara. I paid an extra fee to make the change, but when I checked the ticket, the representative had mistakenly booked me a flight from Istanbul to Oslo and back to Oslo. I’ve called several times, and they assured me they filed a complaint and would get back to me soon, but I haven’t received any response. Each time I call customer service, it adds to my phone bill, and I’ve spent over an hour on the phone trying to resolve this. This is completely unacceptable. I’m seriously considering never flying with Pegasus again unless this issue is fixed immediately.