Voice calling over 3G on the iPhone 6 and 6 Plus devices has dropped sharply across mobile networks in the U.S. and is one-fifth of that on previous iPhone models, as users adopt Voice-over LTE (VoLTE) services, reports Newfield Wireless, a Tektronix Communications company and provider of next-generation Radio Access Network (RAN) geoanalytics.

According to the company, the analysis is based on data generated by Newfield Wireless’ TrueCall platform, which is positioned in the network to provide the visibility and real-time information needed to assess the delivery and performance of VoLTE. iPhone 6 devices are VoLTE-compatible and as a result, U.S. networks have experienced a surge in VoLTE calls since the September launch.

In addition to identifying the decline in 3G voice calls on networks and the subsequent uptake of VoLTE, analysis of TrueCall data has also revealed that on average, iPhone 6 and 6 Plus users are already consuming more 4G data than users on all iPhone 5 devices in U.S. Also, the number of iPhone 6 handsets active on mobile networks is 5x the number of iPhone 6 Plus devices in the U.S. Market.