phones shows incoming call as unknown

[ilevbare 55]

Hi guys please my HTC M8(Verizon) keeps showing incoming calls as unknown, driving me sick that I can't return calls missed....please help

 

[mhinc]

Hi guys please my HTC M8(Verizon) keeps showing incoming calls as unknown, driving me sick that I can't return calls missed....please help

Every single call is coming in as Unknown??
If that is the case, sounds like a SIM card issue. I would get it replaced from your provider. Doubt it's the phone.