San Francisco, Dec 6 : Google Fi, a service by Google that provides telephone calls, SMS, and mobile broadband using cellular networks, Wi-Fi will stop activating non-VoLTE phones from January and it is offering a $100 credit to help customers upgrade their smartphones from the Fi store as well as activate it before December 31. T-Mobile has already announced its own plans to phase out support for non-VoLTE phones starting in January 2021 and Google Fi, as a mobile virtual network operator (MVNO) that doesn't own its own wireless structure, has no choice but to follow suit. Fi works off of T-Mobile and US Cellular's networks, which means its customers will need to buy new phones, reports The Verge. Google has informed its non-VoLTE customers via e-mail about this upcoming change. The limited-time credit will be available to assist customers with a seamless transition from 3G. Subscribers with non-VoLTE compatible devices active on Fi as of December 3 are eligible for this promotion. VoLTE is the current mobile standard that handles phone calls over LTE data instead of 3G. Most older smartphones aren't capable of supporting VoLTE. That means customers with older phones will no longer be able to use their devices once 3G is phased out. VoLTE stands for "Voice over LTE", which is the handling of phone calls over LTE data rather than older 3G tech. Wireless companies are pushing users to upgrade their phones -- 3G networks are largely obsolete, plus VoLTE offers a boost in call quality. /IANS