Error AT Commands testing GPS/GPRS/GSM MODULE V3.0

I am trying to drive the module via USB port (AT commands). I use Coolterm software and I have followed all steps in your tutorial from dfrobot.wiki.... However, the answers due to my AT commands are very stranges.
For example, to command "AT", Coolterm shows me as answer: )-hø
I dont know what can be the problem....
The code is the following:
void setup() {
//Init the driver pins for GSM function
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
//Output GSM Timing
digitalWrite(5, HIGH);
delay(1500);
digitalWrite(5, LOW);
}

void loop() {
digitalWrite(4,LOW); //Enable GPS Mode
digitalWrite(3,HIGH); //Disable GSM Mode
//digitalWrite(3, LOW); //Enable GSM Mode
//digitalWrite(4, HIGH); //disable GPS TX、RX
}

PWR is on, STAT is on and NET is turn on/off constantly.
S1: Comm, S2: USB and S3: GSM

I really appreciate any help you can provide. Regards