Haven’t used it [silent.link] myself. All I know is that all (or some) plans they offer include only incomming-calls, not outgoing. But good point you make about delays. That’s important. Haven’t thought about that myself.
I’m not too versed in it myself yet. You were asking about these services in general, right? Since you wrote “voip numbers”. I’ll keep tabs on your other comment then
It may be exactly this, noticed by Linus Tech Tips: https://www.youtube.com/watch?v=OHKKcd3sx2c
If their solutions don’t work, try this: https://www.youtube.com/watch?v=7JoFi5yXzZk