BAD RECEPTION ON NEW SANSUNG S6 EDGE

I STARTED A NEW CONTRCT WITH VODACOM ON 1 JUNE 2015. I HAVE AN ENORMOUS HIGH CONTRACT DUE TO THE FACT THAT I USE MY CELLPHONE FOR BUSINESS ONLY. I NEED GOOD RECEPTION, A GOOD SIGNAL FOR PEOPLE TO BE ABLE TO HEAR ME AND I MUST BE ABLE TO HEAR THEM AND FINISH A CONVERSATION. I DID ASK THE LADY TO PROVIDE ME WITH THE BEST PHONE WITH THE BEST SIGNAL WHICH WILL ENABLE ME TO HEAR MY CLIENTS AND TO RECEIVE ALL MY CALLS. I RECEIVED THE SANSUNG S6EDGE. THE BEST PHONE ACCORDING TO HER. I STARTED THE NEW CONTRACT WITH THE SANSUNG S6 EDGE. MY CLIENTS CANNOT REACH ME NO MATTER WHERE IN VEREENIGING, I AM. I CANNOT HEAR THEM AND MY CLIENTS CAN ALSO NOT HEAR ME. THERE IS NO SIGNAL ANYWHERE AND MY PHONE BREAK UP WHICH MAKES IT IMPOSSIBLE TO USE THE PHONE AS A PHONE. I TOOK THE PHONE BACK TO VODACOM REQUESTING THEM TO PROVIDE ME WITH ANOTHER PHONE THAT WILL WORK. THEY TOLD ME THAT THE PHONE MUST BE SEND BACK TO HEAD OFFICE FOR REPAIRS. AFTER NOT EVEN ONE MONTH OF MY NEW CONTRACT I WAS AGAIN WITHOUT A PHONE (NEW PHONE THAT WAS ISSUED). THE PHONE CAME BACK AFTER ALMOST 3 WEEKS WITH A REPORT THAT THE PHONE IS 100% NOTHING WRONG. I CAN STILL NOT HEAR OR MAKE ANY CALLS. WHAT NOW??????