charger destroyed the phone

please m not happy with the services we get after we bought the phone AO6 at pep under mtn network the phone worked only for 3 month aftr that i took it back because of was charging the phone aftr that i saw smoke it was burned and i dd returned it where i bought it and they did booked it in and they tel us it was physical damage and the phone was damaged while i was charging it....please want to knw now i cant spend the amount of R1799 the phone was damaged while it was charging..... ime no *** now they tel us that we have to pay the mobey for the phone to come back from welkom where they did send it foelr repairs,how we pay for courier while they failed to fix the phone is this the treatment where get aftr they get sales.. kind regards phillip