Facetime calling people randomly iPhone 6s
My husband's iPhone 6s with the latest OS.10.1.1 is having problems daily of his iPhone facetiming random people and we have even turned off Facetime on the control settings. He is not wanting to even use Facetime. When have taken it the Verizon store and they claim there was nothing wrong with the phone but it keeps happening and extremely embarrassing. Please help!
iPhone 6s, iOS 9.3.5, Verizon phones. Started July 2016