In order to be able to use LTE with the 90% lower radiation than GSM, SIP and tap-proof SIP VOIP apps help
In principle, smartphone users with an LTE tariff can also make mobile calls via various apps. 4G is of course excellent for VOIP apps due to the low latency times and high data rates. The most secure app is called OpusTel, comes from Switzerland and is a phone solution for the iPhone with iOS and for all Android mobile phones such as Samsung, HTC, wiko Huawei and LTE. Furthermore, conversations between two OpusTel app users are tap-proof and free of charge. Only when a landline or mobile network is dialed will call charges be incurred. Usually, however, much lower per-minute prices than GSM mobile telephony with 07x mobile telephony solutions.
Important: Even those who own a modern LTE smartphone or cellphone usually still make calls via the predecessor standards GSM 2G or 3G. 4G or LTE have so far been used primarily for surfing, i.e. for data communication. This is because VoLTE is not yet supported by most LTE smartphones. Modern VoIP apps already help to use LTE networks for telephony. This saves a lot of money every month, as data-only subscriptions are much cheaper. They also radiate 90% less electromagnetic emissions into the head (less than 0.2 watts compared to 2 watts for GSM). You can also continue to surf, chat and use the data network with LTE while talking to OpusTel. GSM callers with 07x mobile phone number lose the LTE data network during the call!