DATA DEPLETED - WHY I DID NOT EVEN USE IT

ON THE 22 SEPTEMBER 2015 @ 6H11 PM I LOADED A DATA BUNDLE @ R 35.00/100MB. WHICH I NORMALLY LOAD SOMETIMES MORE. 1 TO 2 HOURS NOT USING IT THOUGH I CHECKED MY BALANCE AND SAW MY DATA IS DEPLETED AFTER THEIR MESSAGE SYSTEM SENT ME SMS ITS DEPLETED. I ONLY MAKE USE OF DATA BUNDLES FOR WHATS APP ON MY IPHONE 4S. AT ABOUT 8PM AGAIN THAT SAME DAY I LOADED ANOTHER BUNDLE. I TRIED CALLING MTN BUT NO ANSWER. I TRIED CALLING TODAY NO ANSWER. HOW DOES ONE GET HOLD OF THEM IF THEY DONT ANSWER. THEY HAVE THE NETWORK TO USE IF THEY HAVE OR EXPERIENCING DIFFICULTIES OR UPGRADING. YET THEY DON'T ANSWER OR CALL BACK LIKE THEY SAID THEY WOULD. FOR MANY YEARS OF BEING AN PREPAID CUSTOMER ON THE MTN NETWORK I SORRY, NO I AM NOT SORRY THAT I AM PORTING OR SWITCHING NETWORKS. TO A SERVICE PROVIDER WHO TAKES CUSTOMER SERVICE AS THEIR PRIORITY IN THEIR BUSINESS.I NEVER HAD TO CALL OR COMPLAIN ABOUT ANY OF THEIR SERVICE THEY RENDERED. ONLY THAT I NEVER HAD A PROBLEM TILL NOW. I HAVE MY IPHONE 4S MORE THAN 3 OR 4 YEARS ALREADY, NEVER HAD A DATA PROBLEM OR PHONE.WHY ALL OF SUDDENLY NOW. PS THIS IS NOT THE FIRST THIS HAS HAPPENED WITH ME.