Depends on the network. Read the offer terms. The one's I've seen usually have a requirement: call must be at least x seconds long for it to count.
But think of it as any other affiliate network. You are sending them leads they expect to convert into paid leads.
If they are paying you for leads that don't convert into paid leads...
They're paying you more than you're making them.
Why keep paying you?
The network will have high incentive to consult with you, or disable the offer, or do the extreme and disable your account.
Try your best to send them legit leads, but keep going. I stayed on an offer making tens of thousands with a buddy, getting paid per lead, and doubt I made a lot of sales on the back-end before getting kicked off. Your mileage may vary depending on the network/offer.