Cell C is not solving my issue no feedback

I took out a contract \contract buy out\" from Vodacom ever since im with cell c (November 2015) I have weak and at times no signal. I logged cases spoke to customer care and tech support multiple times my contract is unlimited but im not even able to connect to internet or make a call when i do make a call or recieve a call the people on other side cant hear me. I tried all the advise cell c gave me bought a new device did a sim swop correct settings every time they call they did not get through because i have no signal i just get sms say you missed a call phone dont even ring. This is very frustrating for me to repeat the story over and over . I am not a happy customer any more ! "