IVR not leaving messages to Non Iphone users

Anyone see this? Our IVR is not leaving automated messages to NON iphone users(verizon). I verified through sitting on the phone with verizon that they have separate messaging systems for iphones so that has to be something to do with it. The people are getting the call but it is just showing up as a missed call. Other carriers seem to work fine along with iPhones. The issue is that our service territory is probably 70 percent Verizon with a large percentage as non iphone.

Please help