Hackers used my personal email address and credit card info on Zalando (UK)

A user reported receiving a fraudulent 'Thank you for signing up' email from Zalando on their personal email account, followed by a bank notification about a £100s unauthorized order. They denied the transaction, canceled their card, and confirmed no funds were taken, but are concerned about how hackers obtained their email and credit card details together despite not saving card info on retail sites.