There may be MMI/USSD codes to modify the behavior.
For example on AT&T I can dial *#61#+1203XXXYYYY*11*30# where +1203XXXYYYY is the carrier voicemail number and 30 is the number of seconds after which it sends to VM.
Google is your friend. You may also enable call forwarding to a different number of your choice.
When I travel abroad I forward my "unreachable" to a Google Voice number, then I can have my USA phone number ring as long as I have a network connection.
That has been my attitude towards bleeding edge technology since I got my first smart phone. And even then I only got it because my family kept ragging on my to get one. If not for them I would have a brick still :-) So I got the free one. At the time they were giving away the Galaxy S2, the S3 was $99 and I just didn't feel like spending money for technology that I wasn't going to appreciate much anyway. About 6 months later the S4 came out. When it was time to upgrade, the S5 was the latest and about 2 months later the S6 came out. So this time we were going to wait until the S8 was out, but we got an offer to pre-order the 8 and get a Gear VR FOR FREE!
So I am happy that I (for once) have the latest, even though I probably would have been happy with the not-latest. It's a very nice phone. But the VR is really something. I have not much time for game playing, but I'm happy to have a little diversion. I thought we would get one VR, but we got one for each phone. Kind of hard for me to complain about Samsung after that.
When you're left out of the club, you know it. When you're in the club, you don't see what the problem is.
I am Green-Eyed.
I broke down and gave up and now I use the visual voicemail. It actually is much better and faster than the regular voicemail. You don't have to dial in, you don't have to sit thru it telling you what time they called, the number it came from or the duration of the message. As soon as you click on the voicemail, the voicemail starts playing and it has a scroll bar so you can skip forward to wherever you want, forwards or backwards.
If you haven't already, I definitely recommend giving it a try.
Package disabler pro is legit. I am able to use my phone as a hotspot for free now. You do have to be able to connect to a wifi network to turn on tethering, then you turn off the wifi and you have your own hotspot.