Online payment

An amount of R1499 was deducted from my account with the reference "online purchase." I am using a new card and do not have the banking app yet, so I am unsure how this transaction was approved without my authorization. I tried speaking to an agent over the phone, but they said they could not assist or verify my account. The agent on WhatsApp suggested I search for the company that debited my account using the reference, but it only says "online purchase." How could this happen?.. funny part my card is not even 5 days old and now this