Raspberry / SIM900A module calling problem

Question

I am trying to call my phone from raspberry pi through SIM900A module , I interface the wires well and the module blinking . the python code run and say that its calling, but my phone don't ringing ? this is the code

import os, time

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)

port = serial.Serial('/dev/ttyAMA0', baudrate=9600, timeout=1)

port.write(b'AT\r')

rcv = port.read(10)

print(rcv)

time.sleep(1)

port.write(b'ATDxxxxxxxxxx')

print('Calling…')

time.sleep(30)

port.write(b'ATH\r')

print('Hang Call…')```


The output is :
 

b'T\r\r\nok\r\n'
calling...
Hang call...

The mincom give me a response OK for AT command 

Answer 1

You didn't finish your ATD command with carriage return (\r) character.

It's always good practice to read answers that modem sends back to you. By ignoring them, you don't really know what your problem is, you only know that there is some.