MZANSI4U-Unauthorised debit order **** sms

An amount of 99.99 with the reference MBSMZ ********** 2 will be debited from my Nedbank account on the ********** 9. I have not authorised this debit order. I just received an sms with a cell phone equiry ********** 430. This number rings but no one picks up. Plz help me