1.
If you have received an invoice from Apple, it will be stated on the invoice for what you have to pay.
Tap on Report a problem on the invoice.
or try to -> Request a refund for apps or content that you bought from Apple.
Request a refund for apps or content you've bought from Apple – Apple Support (UK)
If you have requested a refund, you must wait until Apple has approved. Then you will receive a message from Apple.
Refunds are not guaranteed. For more information, see the Terms & Conditions.
2.
If the invoice is not from Apple, was the money deducted by a stranger?
Contact your bank, they can find out who (name, address & account number) has collected the amount from your bank account, and when.
Depending on your bank, they can collect the amount back within 30 days.
Ask also your bank to block your card, ans ask a new card.
Also report to the police.