Yazıyor App Has No Customer Support Contact

After downloading the Yazıyor app on my Android device and signing up, I discovered that an annual subscription had been automatically assigned to me without any clear notice or confirmation on my part. I canceled this subscription on June 19th, but the $28 charge I was billed has not been refunded.
I have no order, transaction, or invoice number related to this charge, and I was unable to find any phone number or support channel — either within the app or through Google Play — to reach customer service. This situation has left me doubly wronged: I was switched to an annual subscription without being properly informed, and now I have no way to get in touch with anyone to resolve it.
I am demanding that my annual subscription be fully canceled and that the $28 I was charged be refunded to me immediately.