iTunes payment

To stop the subscription : View, change, or cancel your subscriptions - Apple Support

For a refund obviously nobody on here can do that. Purchases are considered final as you know, but you could try the 'report a problem' page to contact iTunes Support and see if they will refund you as a one-off : http://reportaproblem.apple.com

Or you can try contacting iTunes Support via : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)

I still do not understand how can I receive the money back. Please, advise, what should be done from my side?

Have you contacted iTunes Support ? If not, read my previous reply

Please, advise if my request for money return was received?

You know that I'm just a fellow user, but if you haven't contacted iTunes Support, obviously no.

How long it will take to review and solve the problem?

iTunes Support should reply within 48 hours.

This should work for contacting Support : https://support.apple.com/en-euro/contact

Or you can try : https://www.apple.com/emea/support/itunes/contact.html

What country do you live in, and therefore what country is on the account ? Contact methods are likely to vary by country and topic.

If you've contacted them it can take up to 48 hours for them to reply