Vodacom cannot repair a Samsung phone

The Samsung S5 Cell phone lost signal. People would phone me and the phone would be switched on but the caller was informed the phone is switched off. Submitted to Vodacom The Grove for 7/8 weeks - not repaired. Phone still loses signal but now echoes on my side. Submitted to Vodacom Menlyn - 4/5 weeks later still not repaired. Phone still loses signal but now echoes on the callers side. Submitted to Vodacom Menlyn - 4 weeks later still not repaired. Phone still loses signal but now echoes the callers side. Submitted to Vodacom Menlyn - 4 weeks later still not repaired. I think a new phone is the only way to resolve the issue but Vodacom refuses.