They only give the free trial to people who can actually pay.
It sounds like you were using a debit card.
According to Google, 30 TRY Turkish lira are only worth $0.87 in US Dollars. I think it was probably just a nominal amount to be sure that you can pay if you decide to subscribe.
If you don't want to subscribe, be sure to cancel before the week is over.
i just created my account and was offered a free trial premium for a week, i accepted and entered my credit card details but it tries to withdraw 30try from my bank account upfront. i declined transaction, are you sure this is free?