I have done all those steps and rechecked them again. The problems I'm having are intermittent...
(1) at least once a day when I try to make a call, any call, I don't hear a dial tone. So I try again and no dial tone. So I try to call different #'s and get no dialed tone with them either. Then I turn phone off and on again and make the same call. Then I hear dial tone and call goes through. It doesn't matter what phone # I'm calling.
(2) I've been told that sometimes my phone goes right to voicemail and it doesn't ring. I don't turn my phone off and it's always charged. If I then try to make a call out I get no dial tone which tells me that somehow this problem is the same as (1). Again, if I turn phone off and then on again then I can receive calls. I've had this phone awhile and know that all settings on the phone are correct and software is up to date. This has all just started happening in the last couple of months and is intermittent. My husband started having the same problem when he had his iphone7 for awhile.