spectrum time warner cable spectrum charter not providing 100 mbps on download speed Charlotte North Carolina

SPECTRUM/TWC IS SUPPOSED TO BE PROVIDING ME WITH 100 MBPS DOWNLOAD SPEED FOR MY COMPUTERW/ WIRELESS WIFI ,THAT THEY  GAVE ME FOR FREE, AND HAVE NOT COME CLOSE. I HAVE RUN A TEST ALMOST DAILY FOR 3 WEEKS NOW , AND THE NEAREST THEY HAVE COME IS 78. IT HAS EVEN BEEN AS LOW AS 61. I HAVE CALLED TWICE. FIRST TIME I WAS TOLD NO PROBLEM. THEY SENT ME A LETTER SAYING THEY WOULD BRING ME TO 100. AFTER WAITING 5 DAYS WITH LITTLE INCREASE, I CALLED AGAIN. I WAS THEN TOLD THEY ONLY HAVE TO PROVIDE ME TO WITH-IN 70% OF 100. AFTER THAT CALL , MY SPEED ACTUALLY WENT BACK DOWN TO72, WHITCH IS WERE IT STARTED.