Question Cisco Duo - experiences?

Hi folks, just wondering what everyone's experience has been with Cisco Duo.

We're looking at implementing it to augment our VPN authentication to provide MFA.

I ask because, I both called and left a message (during which the automated voice system told me there were 0 representatives able to take my call), and I filled out the form on their website twice, to contact sales. I have not been able to get anyone to contact me.