You can change network mode. This app works on all android devices. If your phone/carrier supports VoLTE, LTE only settings might help you from dropped calls. You can change network mode at "Set Preferrend Network Type" when you launch the app. If you want to use 3G Only -> WCDMA Only If you want to use 4G LTE Only (VoLTE/IMS should be turned on to receive/send calls/messages) -> LTE Only Thank you.