I think you have a great point. We have had this no-ring/no-VM issue with my husband's Galaxy S5 Active on AT&T since we purchased it last August 2014. We have changed SIM cards, new phone, rebooted to no avail. We have been talking with tech support for the past 2 weeks and I keep telling them to google it and many people have this same issue on several phones and several carriers. Today, I tried this test...
1. Called my hubby's phone (had not been used today yet). It rang several times then went to VM. Did not leave message. Nothing on his phone.
2. Called again, straight to VM. Did not leave message. Nothing on his phone.
3. Called again, straight to VM. Left message. Nothing on his phone.
4. Called again, straight to VM. Nothing on his phone.
5. Texted. Waited but no ding on his phone.. I may not have waited long enuf.
6. Called again, VOILA!!! It rang on his phone!!!! Immediately thereafter, his phone dinged that the text from #5 was received...
7. Called again, rang on his phone.
8. Waited 1 hour. Phone rang just fine... Will now wait 2 hours and see if it goes into lala land again. Trying to find the amount of time before it goes into "Lala/sleep" mode again.
I have an older Moto X and do NOT have any of these problems. That's why I am stumped. Does the Galaxy use different technology?
It appears that the text message from me to him "woke his phone up". Btw, we changed his VM message to ask people to text him and that his phone is not always ringing thru. Hope this helps someone else... This has been sooo frustrating!!! Also, we are sitting in the same room, with WIFI on, doing these tests.