It's a work in progress. Verizon recently gained a waiver for Wi-Fi Calling to be used on their network, although for now requires the Messages+ app to be installed, in addition to the "Advanced Calling 1.0" feature to be enabled on your line.
In the near future your iPhone should be gaining native Wi-Fi calling support. Expect this probably in the next iOS 9 update.
Thanks, it's been hard to get a straight answer from Verizon. i've gotten several different answers from definitely yes to definitely no to yes under certain conditions.