Complaint(unhappy customer)

I would like to lay a complain regarding the service I got this morning at spar retail crossing.

We work the same retail crossing,we came in to buy a bottle of coke,paid at the till points .we left the store,the security guards came running behind us demanding a receipt. I was surprised coz they never ask for a receipt. Other customer's left the store without being asked for receipt. Am I treated as a ***** ? I don't feel like shopping anymore at the store becouse customer's are not treat equal . We can't shop while people are running behind us thinking we are suspects. This service I got it's unbearable.