Ask HN: Has anyone ever set up a free conference call system?

So a little weird question, but we are working on something that needs the same foundation as a free conference call system. Has anyone ever set one up before or worked for a company that has? Would love some advice and/or guidance on how to get the basic setup working.

OR

If you happen to work for/be a founder of a service would you be interested in chatting about partnering?

I know this is not the typical post on HN, but was not really sure where else to turn.