Q: my iPhone doesn't ring. I see the missed calls

Do you have Do Not Disturb enabled?

Use Do Not Disturb on your iPhone, iPad, or iPod touch - Apple Support

Try checking in your notifications to see if you have turned them off somehow. You can check this by going to settings, notifications, and phone. There you can change if you will get a notification, if it will show up in your notification center, the sound when you get a call, if the page app icon will appear or not, if it will show on your lock screen (in your case I would turn this on), and wha type of notification you will see on your iPhone (banners, alerts, or none). You could also check the phone setting when you enter the settings app. But I don't think that area will help fix the problem you are trying to fix. Hope this helps!!!