After 3 weeks iPhone still faulty

I collected my iPhone 6 yesterday from the Phoenix Branch.<br> Reference number CLC***.<br> I sent the phone in for repairs because the software froze. <br> When I got to the branch to pick up my phone the battery was flat.<br> I signed the release document & was told to charge my phone as it is fixed.<br> Upon charging the phone & switching it on the phone is vibrating when I hold it in my hand for absolutely no apparent reason. It went in for a software fault & now it seems like a new hardware fault. <br> After 3 weeks to get back my phone back with another fault is totally unacceptable.<br>