please help to either fix or upgrade my phone. I am missing medical calls because my phone is going to voice mail and not accepting these important calls please help

• Check your DND status - Settings > Do Not Disturb; Use Do Not Disturb on your iPhone, iPad, and iPod touch - Apple ...
• Check BedTime Status - Clock App; Use Bedtime to track your sleep on your iPhone - Apple Support
• Check your Sound Volume; Adjust the volume on iPhone - Apple Support
• Check your Ringer switch; If you hear no sound or distorted sound from your iPhone, iPad, or ...
• Check Call Audio Routing; Call Audio Routing Bluetooth / Speaker / Automatic
• Check Auto Answer Calls; Turn off Auto Answer Calls
• Check Connection with Bluetooth Audio; Stream audio from iPhone to your hearing devices - Apple Support
• Check whether in Headset Mode; If your iPhone is stuck in headphone mode - Apple Support

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This is Apple Support Community forum, for user-to-user interaction for information & idea sharing between users, if need be, extend support on technical know-how in handling Apple products from more experienced fellow users, This is not the right forum to discuss with Apple Inc.