I have a problem, that has become more frequent over the last several months, of calls not coming through properly. My phone never rings. People say it sends them straight to voicemail when they call. The funny thing is -- it's only calls from people I WANT to talk to. Every telemarketer in America seems to have no problems getting through. This has been going on about a year. I contacted customer service and got basically nowhere. They said upgrade my phone. Due to other circumstances, I did just that. This brand new iphone 6s plus is STILL having the same issue, so I know it's not the phone -- it's the service. I've talked to other people with this same problem. What can I do to fix it?