G-MoN (Pro) does not send any personal data like IMSI, IMEI or telephone number out of your device.
Your imported cell data is only stored on your device and will not be send out of your device.
G-MoN Pro uses Firebase Analytics with non personal information in order to detect the net monitor capabilities of different devices.
TheFirebase Analytics privacy license can be found on https://firebase.google.com/support/privacy/ You should note that the analytics currently can not be turned off.