Blue Connect,they not responding on my matter

My name is Nozipho Mkhize I bought cellphone blackviewA80,within contract from Blue label connect,my phone is 3 months old so it's lost all the sound,didn't drop it or wet it,just stop 2weeks back,tried to phone them report the matter,and saying I'm not happy about the phone and it's very slowly,and the lady sold to me said it's Sumsung,they said I can cancel the contract and open another one when it's done,they never phone mefor that,I phone they yesterday they told me the Cancelling Department keep ignoring my matter so I need help pls