Been having this issue for months now! More often then not, my phone doesn't receive calls. Goes straight to voicemail without me knowing a call was even attempted. Happens mainly at home. I can make calls and receive texts fine. Last time I checked, a mast isn't working as it should in my area, but others in my house do not have this issue (also on the same network as me). I have swapped my SIM last week, issue still isn't solved. Signal is very weak, but again, can make calls fine and my network provider says service is 'good' at my Postcode. Cannot try SIM in another phone as any time I get someone to call me to test it it, of course, works. It is not just certain phone numbers having this issue, it is all of my contacts, and yes it also happens outwith my own home, but it is mainly here. Yes, I have done all the usual troubleshooting such as restart phone, 'do not disturb' is off, airplane mode on and off again, swapped my SIM etc.