Rude hotel manager

I made a booking on this hotel for the 23rd of May checking out 24th of May via an app called Booking.com. According to the app, cancellation on this hotel was free of charge. Due to personal reasons, I had to cancel the booking before they even took the money from my account, a few hours later, they took money off my account. I called In to ask for a refund and they agreed to give the money back. Now they’re ignoring my calls because they haven’t refunded me. They give me the same story all the time.