Telkom mobile call quality appalling

I have been a Vodacom customer for over 20 years but recently changed service providers to Telkom due to their excellent Flexon packages. Unfortunately I can no longer use my phone for cellular voice calls. The change in quality is so dramatic that I am actually considering going back to Vodacom. The only way I can speak to someone on my phone is via WhatsApp or Skype. The quality of the cellular calls is absolutely atrocious. I cannot believe that this is acceptable and would like a senior Telkom consultant to contact me to test the service and if this is the actual normal for their cellular network I would like to seek relief so that I can get back to a service provider that actually provides a voice call service. Please help.