Voice over WiFi

Mobile 4G/LTE signal is weak at higher floor ? - Voice over WiFI (VoWiFi) is exactly what you need for better Mobile signal reception.

Below are extracts from https://www.maxis.com.my/en/faq/network/mobile/vowifi/

Voice over WiFi (VoWiFi) is a term typically to describe the delivery of voice call services using Voice over IP (VoIP) technologies from mobile devices connected across WiFi.

Most mobiles operator will be provisioned with VoWiFi service with the exception of customers on multi SIM one line (MISM). Do Google to check if your phone is compatible with VoWiFi.

Most notably, Voice over WiFi (VoWiFi) allows user to receive and make call over a WiFi network on mobile line, when mobile signal is limited or absent. It is a simple direct dial, as long as you are having a compatible phone and have turned on WiFi -Calling at your phone.

Beside this, it will be a seamless handover where user stays connected in an active call when moving to a strong 4G coverage but weak in WiFi signal.

How to enable VoWiFi on my device? Different phone may have different steps to enable VoWiFi.

In general:

From your phone, click at SETTINGS > MOBILE NETWORK > Enable WiFi Calling/VoWiFi

If your phone does not have this option, it may not support VoWiFi, do ensure that your phone is updated with the latest software.

VoWiFi while roaming is not available.