How do I change the number of rings before voicemail activates on a Samsung Galaxy J7 V?
The voicemail ring time is set at 30 seconds at the system level and can't be changed.
As Ann154 said, the time is set at 30 seconds and can't be adjusted. You may want to try a different ringtone (I use a song that plays continupusly until it goes to voicemail) if the issue is that it there is not enough time or rings.
If callers are complaining that its too long or short before voiceamil kicks in, there's not much you can do. It's set at 30 seconds.
