How can I get a refund for the unauthorised charges on Coursiv subscription?

It looks like you’ve been scammed. Apple is not a bank. It does not approve or decline transactions. Only the bank that issued your payment method (credit or debit card) can verify and approve or decline transactions. Apple Pay is just a means by which the transaction and payment information is encrypted and securely sent between your bank and the merchant.

If the merchant scammed you, you need to report the fraud to your bank. There is nothing Apple can do in regard to a refund.

By the way, you also need to read things carefully. You say, "it said that i have to pay 0.71 USD for subscribtion" It does not say that, what it says is it costs 0.71 per day for a 4 week subscription. That would be $19.88

I need a refund on an unauthorised debit of €49,99 twice on my account I’ve been contacting COURSIV customer support but to no avail.