Mobile Voice Search issue on multiple devices

[Mossback]

With Verizon carrier and Google Microphone for Samsung Galaxy 7, Motorola Droid, and an iPhone, not receiving the same positive rankings in Voice Search as same search on ATT Samsung S4 or search on PC. The search terms are for a local listing business and it does not show up at all on first several Google pages with the Verizon phones and Google Microphone. Anyone else experience similar problems? SEO has been optimized regularly including long-tail keywords. I am thinking the issue is either the carrier (Verizon) or the app (Google Microphone). Any thoughts would be much appreciated.