My iphone 6 gives a busy signal when anyone tries to call me. The ipone 6 does not go to voicemail either. I have turned phone off and on several times. I have checked airplane mode. I have the most recent updates from apple as well as from Verizon. Verizon check says I have no issues. I have no blocked calls set. Call forwarding is disabled. My iphone is 100% charged. Ringer is not muted. I have not dropped the iphone or gotten it wet. Help!