The best phone conversation spy software

Wow some comments....

OP check labour practices. Once you've done that there are enterprise solutions for what you need. Blackberry BES 12 or Good both achieve what you want.
BUT check labour laws. And beyond that, regardless of laws, the only fair and ethical thing is to let the employee know of the monitoring and signing a consent.
That's what we do in the agency where I work.

Sent from my gorgeous sexy white BEAST of a Note 4 ❤
 
You will probably get sued if you do this. Did you put your plan, to monitor their conversations, in writing to your employees? You will need to do that to escape a jail term. Ask NSA how they do it. :)
 
You need to trust the man you employed. And you have to make sure it's legal to do that even in company time to avoid law sues.