How to fix 'int' object has no attribute 'astype' error when sending WhatsApp messages to large number of contacts using Python and pandas?

AttributeError: 'int' object has no attribute 'astype' in automatic WhatsApp message sender script

The following is an automated WhatsApp message sender script I partially developed. I tried the following script and it worked fine with an excel with 5 numbers in it. However, I tried upscaling it to 1700+ numbers, and I get the following traceback:

Traceback (most recent call last):
  File "c:\Users\MSI\Desktop\AutoSenderPY\main.py", line 9, in <module>
    cellphone = data.loc[i,'Cellphone'].astype(str)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'int' object has no attribute 'astype'*

The script is the following:

import pandas as pd
import webbrowser as web
import pyautogui as pg
import time

data = pd.read_excel("book1.xlsx", sheet_name='sheet1')

for i in range(len(data)):
    cellphone = data.loc[i,'Cellphone'].astype(str) 
    
    message = "Test Message"
    
    web.open("https://web.whatsapp.com/send?phone=" + cellphone + "&text=" + message)
    
    time.sleep(5.5)           
    pg.click(1230,964)      
    time.sleep(1)            
    pg.press('enter')       
    time.sleep(2)         
    pg.hotkey('ctrl', 'w') 
    time.sleep(1)

Why is that happening, and how can I get it working for those 1700+ numbers?

Try using -

cellphone = str(data.loc[i,'Cellphone'])

I think loc returns a single element of type "numpy.int64", calling the "str" should be enough.