My account was used without me being aware but RCS should know

Please help me urgently. I received the statement and it shows that on the 29.10.2018 i bought something only from Glocell that costs R999.00. That purchase was never done by me, i dont even remember the last time i used this account. I received SMS same day from you saying "We noted suspicious activity on your RCS card and blocked the card for your protection. Reply 1 and we will call you now to unblock your card" Please help me ASAP. How can i system not send me notification that i'm buying like it use to? Your SMS claim that you blocked the activity. Are you no longer using both card and ID when account holder do a purchase? Please investigate and refund my money ASAP.