S5 mini loss of connection issue never resolved

In December 2014 I renewed my contract and received an samsung s5 minil. I constantly lose signal and have to restart my phone to send and receive calls or messages. I have taken it in for repairs 3 times at Vodacom Sandton City, and after all 3 times the same problem continues. It is very inconvenient having to borrow a phone while my phone is in for repairs and then having to set up my phone again and again. I am paying for a phone which does not work. The Vodacom repairs team clearly cannot fix the problem and all they can tell me is, \If the problem continues then bring it in again for us to have a look."How many times do I have to go in and out of the Vodacom store? <br> After doing some research"