Preply Refund From August 7 Still Not Credited to My Account

I made a payment on Preply to take lessons with a specific teacher, but after the teacher closed their account, I requested a refund of my remaining balance. On August 7, I was informed that the refund had been processed, yet the amount has still not been credited to my account. I have contacted Preply customer service multiple times about this issue, and each time I was told to check with my bank. However, my bank confirms that no such payment has been received. This is the first time I have encountered such a problem, and the prolonged process has caused me serious inconvenience. I request that my refund be deposited into my account immediately.