According to tech support there are only two ways to forward calls: The *72 function on the phone, and by calling Verizon. This does not appear to be the case.
I have an iPhone 5 and my wife has a 5s. For the second time in three months, both our phones stopped receiving calls and started forwarding to random voice mail services at the same time.
When I discovered neither of our phones was receiving calls this morning (outgoing calls still work fine), I called tech support. Support told me one (but not both) of the phones had call forwarding turned on. It was forwarding to a random number in Arlington, VA - we live in Atlanta. When the tech removed forwarding on one phone, it fixed both phones.
What causes spontaneous call forwarding? Why do our phones spontaneously stop receiving calls, seemingly at random?