MKR 1300: US915 support

Can you please explain where this reset happen when doing the initialization like follows:

void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
while (!Serial);
// change this to your regional band (eg. US915, AS923, ...)
if (!modem.begin(US915)) {
Serial.println("Failed to start module");
while (1) {}
};
Serial.print("Your module version is: ");
Serial.println(modem.version());
Serial.print("Your device EUI is: ");
Serial.println(modem.deviceEUI());

int connected = modem.joinABP(devAddr, nwkSKey, appSKey);
if (!connected) {
Serial.println("Something went wrong; are you indoor? Move near a window and retry");
while (1) {}
}

}

I've gone through the MKRWAN library and the only one I found has been when doing the begin, but then immediately there's a changeFrequency so I'm guessing that after the reset the frequency is changed...

When trying this code I'm expecting to see the key exchange on the gateway (whatever the payload for that is). I am using a Raspberry Pi3 with a wired dragino shield and I have seen the key exchange or authentication when using the EU868. So I'm guessing that this reset is done somewhere and I'm not able to see it.. Also What's the exact frequency for the US band? is 902.3 or 914.9 I'm trying also to tune the node with the 915Mhz I preset at the GW.

Kind regards!