Samsung handed in for repairs under warranty. Cannot get the phone back

Our Samsung was handed in on 03/08/2017 at Samsung (Pandodox Pty Ltd) in Menlyn Pretoria order ********** 989. We received a message on 13/08/17 that the phone was ready for collection. Since then we have been trying to get the phone. We have now visited the shop 3 times and every time it was said that the phone was on its way from The Grove to Menlyn. Now it is apparently still with the technician. No one is returning any of our calls. This is extremely poor service. Please assist.