Pay per call TV is an arrangement to buy television advertising but instead of paying per commercial airing (spot) you pay per call received from said television spots running. The organization running the spot would be incentivized to use a very enticing message that garners calls with even the slightest hint of interest while the advertiser would rather use a very focused message with only the best of the best high intent calls.
The pay per call model puts some of the risks in the hands of the television networks as opposed to just the advertiser if no response is generated from the commercials.
If the commercial and optimization are done really well, then a lot of calls are generated in an efficient manner and the television network can make a lot of money from sold calls.