Sending UDM message from Raspberry via SIM900a GPRS module in python. 1nce provider

I'm trying to send a UDP message via GPRS service from Raspberry but nothing happens. Here is my code. Any advice? Sorry, but this is my first question on StackOverflow. Thanks

import time
import serial

def receive(ser):
    print("READ:")
    time.sleep(1)
    data_left = ser.inWaiting()
    while data_left > 0:
        received_data = ser.read()              #read serial port
        time.sleep(0.3)
        data_left = ser.inWaiting()             #check for remaining byte
        received_data += ser.read(data_left)
        print(received_data)


ser = serial.Serial("/dev/ttyS0", 9600)
time.sleep(1)
ser.write("AT+CGATT = 1".encode())
receive(ser)
ser.write("AT+CSTT=\"iot.1nce.net\"".encode())
receive(ser)
ser.write("AT+CIICR".encode())
receive(ser)
ser.write("AT+CIFSR".encode())
receive(ser)
ser.write("AT+CIPSTART=\"UDP\",\"100.22.34.22\",8000".encode())
receive(ser)
ser.write("AT+CIPSEND".encode())
receive(ser)
ser.write(("{\"testo\":\"12345\"}" + chr(26)).encode())
receive(ser)