Card keeps blocking

I got my personalised card about 2 months ago. My salary was paid in the 25th May. With my first transaction this month, i was most embarassed standing at a garage, the attendant filled my car with petrol, but when i gave my card, i couldnt pay because my card was faulty/blocked. I had to go into the branch to unblock it. Went straight to a clothing shop from the branch, once again my card did not work and i had to leave my goods. Next day went in to the branch again, they unblocked it. Next day, AGAIN i could not make a purchase and had to leave a shop with a red face! Friday i went in to the branch AGAIN, gave me a new card. The card worked for one purchase, again blocked after that! I am ever sorry i moved from Standard Bank! Sooo frustrated.