4 Garmin Forerunner 70 ladies replaced since 2011

I have had 4 Garmin Forerunner 70 ladies replaced since 2011. I bough the watch for approximately R1700 and every time the watch has not last me for more than 6 months. Garmin used to be in Durban and every time they were happy to replace it with a \new"watch. They are no longer in Durban but in JHB. My 4th watch was replaced I July 2014 and had to wait a week. I am training for the Comrades and cannot afford to wait a week every time the watch is faulty. I rely on the watch with every training session. I have sent Garmin a email on 12th February 2015 and to date has not responded. I have asked them to refund me so I can purchase a reliable watch or they can replace it with a more reliable watch as it has been 5 years and they just keep giving me a \""new\"" watch that doesn't last me more than 6 months. Please help."""