Can you block a user from setting up a conference call?

Can you block a user from setting up a conference call? Site is using Sangoma S500 phones

That will depend a great deal on what specifically you mean by ‘setting up a conference call’. Are you talking about disabling the conference button on the phone?

When users have a call on hold and answer a second call, they are accidentally conferencing the two calls together.

I am having this exact same problem!! Did you get this figured out? And what was the solution. I am having this happen at a medical facility where nurses are accidentally conferencing two patients together which can be a BIG problem.