If you have a Google account I would strongly suggest you at least try out getting a Google Voice number and then playing with the Hangouts app on iOS and possibly under Chrome. One can also access the Hangouts functionality at hangouts.google.com.
I do not believe a hold function is available, but I do know that a mute function is. I also don't know if one can use it to do multi-way calling for phone calls, but I know that one can do so for the built-in video calling function, but that applies only to others who have Google Accounts.
My business number is a Google Voice number that I access exclusively via Hangouts. One can also use the native Google Voice webpage, too, but I haven't done that in ages because, for me, Hangouts is a superior interface.
Since it's free and not all that complicated to set up it's worth giving it a whirl and reporting back on what is, and is not, accessible via the various interfaces. If you want to talk to me off-list about this you know how to reach me.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.
~ Mark Twain