No Network- (Since last week Thursday)

Cell C is becoming worse and worse with the network.- having problems with my cellphone since last week Thursday (4days) i have a 4 month old LG 3G beat which means that it is still brand new. But i don't have ant network. It just says no service, I have tried putting my sim card in another phone it will work for a few minuets and then i have to search for network again.I called 140 as well they put me through to the Tech department i was told there is nothing wrong everything seems fine on the system I have taken my phone to a cell c store on Saturday the 14 November 2015 and was told that there is nothing wrong with my phone. . They then gave me a new sim card BUT IT IS STILL DOING THE SAME THING!!!! WE PAY FOR A SERVICE BUT WE ARE UNABLE TO USE IT!!! <br> <br> This has gone on for too long now!!! Cell C YOU NEED TO FIX YOU NETWORK!!!! <br> <br> ANGRY!!!