Samsung Galaxy S6 Edge — Calls going direct to voice mail

Question

I'm having a problem of calls going direct to voice mail without the phone ringing - even when I have good reception.

I've shut it down and restarted dozens of times, did a factory reset, and even had a new SIM card put in. 
Still does it.

It doesn't do it all the time, but it's with increasing frequency.

At times it doesn't even go to voice mail.. the caller just gets a fast busy signal.

Is anyone else having this problem?

James Watson · Answer

Voicemail will be left when your phone is off, has no reception, or can't be answered. So, I think you had better contact your carrier to verify whether the mobile signal quality is poor or the SIM card is not good enough.