British Town Demands Payment for Cancelled Course

I went to the branch in Eskişehir to inquire about the prices. Of course, I was called "come in" four or five times a week. When I went there, we discussed the prices, and I approved them. I signed and paid a deposit. After I completed the signature and deposit process, the representative there, although we had agreed on Mondays and Wednesdays, said, "I must have seen it wrong, Mondays and Wednesdays are not available." Then they said, "Okay, I will handle it and get back to you." I confirmed and left. Later, they called my father asking for payment-related issues and reached out to him for one or two weeks; even a month later, they added my father to a WhatsApp group. How does an English course that didn't contact me in any way manage to reach my father and ask him for money? I had stated there that I was not available on Mondays and Wednesdays. Later, I preferred not to participate. However, the institution constantly insisted, "join." But I don't want to, I won't fall into the same mistake again. Today, a debt collector called and said that if 23,000 ₺ is not paid within a week, legal action will be taken. I had already paid 1,000 ₺ for a course I never attended. Now they are demanding 23,000 ₺ from me. I had two witnesses with me when I signed, thank God they saw and heard everything. I demand that my problem be resolved.