Incoming phone calls

I have an iPhone SE. He has version 13.3 iOS. Ever since I upgraded to version 13 my phone sometimes does not ring but displays a missed call message. Yes the volume is up in all settings are as they should be in receiving a phone call. When it does this the caller can leave a voicemail. I could be sitting here with my phone in hand when this happens. Is this related to the upgrade of IOS 13 on my IPhone SE? I'm missing important calls. Can anyone help or direct me to who can?