Vodacom bad service

Hi my name is Nokulunga Tabane, I am very angry with vodacom, my phone has a problem when I speak the next person complains that they cannot hear me, it keeps on going down like I am far away, then I have to drop and call that person again, secondly when I charge it it becomes very hot and it drops the calls on its own whilst still talking. In November I took it to Samsung and they have changed the mother board it still giving me the same problems then I took it to vodacom it came back with the same problem , I have sent this phone 3 times for repairs but it comes back with the same problem, right now I called customer care and I spoke to Thapelo who put me through to Cynthia and Cynthia says I must take it back to Menlyn for the 4th time for them to escalate the problem.i am frustrated and I am loosing business because of this, please advise on what to do , I even wrote an email to vodacom complaining they never responded. I don't know how many times must I take this phone for repairs.