I've used Jami regularly for a while now and for me it's been as reliable as Skype.
But your experience may vary, because you are a different person calling different people.
It's difficult to say a VOIP service is "reliable" vs "non reliable", because there seems to be a lot of variation between people's experiences.
For example, I have never, ever, been able to get Jitsi Meet to work *at all*. But I know a lot of people use it, so I still recommend people try it.