Outrageous servious

I have a cellphone contract with Vodacom and the device I have is a Huawei P9 lite. Ever since my phone did the software upgrade it switched off and never came back on. I handed it to Vodacom repair centre on Old Fort Road in Durban and the gave a brand new device (same model). the same thing happened with that one, I gave it back and they gave me a new one (same model). They have given me 4 brand new devices and all have the same problem. Now they refuse to except that this model phone has a fault. they refuse to issue me a different device. so now i am stuck paying for something that i do not have. I advise everyone not to get this phone as has a fault and do not use vodacom.