royal mark **** R115.00 unathorised transaction

I received a text on the 26/04/18 notifying me of a transaction that will take place on the 02/05/18 for an amount of R115.00 ref:ROYALMARKOROYALM ********** ********** . I do not know these people and I have never authorized such transaction to take place.02/05/18 I wake up to a text that says R115.00 is debited from account , I immediately reversed the transaction and blocked future transactions from taking place.