I use Free Conference Call almost daily. It's quick to access, and is easy to use for a wide spectrum of user ability. I often use this product to switch presenters so I am able to see other people's screens when filling out applications, user issues, or to look at the same report at the same time. It's great for setting up a quick on-the-fly meeting, and doesn't give me issues even when other users have a tough firewall, like other products.
The one thing I wish I could do is copy/paste from my Account Information screen without it turning into a table. Sometimes, I don't want to do a full-fledged invite, but instead I want to just copy/paste my conference line into an email, or an invite. Currently, when I do that, it formats it into an odd table-image that is difficult to change.
The one time I had to use the VOIP, it was super-annoying whenever I pressed "mute" because a little audio script would play, and I missed some of what was said in the call every single time. If that wasn't a feature, I would use the VOIP every time.
Do not pay for a different service - everything is right here!
My job is 100% remote, so I use Free Conference Call to host conference calls, share my screen with others, and have them allow access to their screen. We are solving distance issues, account registration, data analysis, care coordination and more. We are also closing the gap when it comes to user accessibility, and involving large groups of people on the same project.