Please make sure to use a stable and a good internet connection as the quality of the call is highly dependent on the quality of the connection. Try the connection via 3G/4G/LTE, as well as via WiFi, to see if any differences pop up.
In the case of the Apple operating system iOS, you may have disabled the ability of Talk360 to use your microphone.
Please go to the iOS settings application. Select ‘Privacy’ followed by ‘Microphone’. Switch the microphone on for Talk360. The receivers of your call should now be able to hear you.