IPhone 6 Plus and 7 locking up I had a locking up problem on my 6 Plus and after talking to a Apple Tech higher up the food chain he said it was a software bug somewhere and that I would need to reset and start over as a new phone. Instead I bought a 7 and started over with my 6 as a backup. The 7 worked fine until I turned off the Icloud Contacts at which time the problem is now on teh 7 too. I even reset it as a new phone and teh problem continues. What can I do?
you could try downgrading to an older version of ios. you would need to put the device into what is called DFU mode or recovery mode, see here:
https://www.youtube.com/watch?v=15qaTA4lQPc

you will also need to download the version of ios you want from here 
https://ipsw.me/

once downloaded, put your device into dfu mode, open itunes, hold shift and click restore, browse to where you downloaded the firmware file and install it