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

以下是我部分开发的自动化WhatsApp消息发送者脚本。我尝试了下面的脚本，它与Excel中的5个数字很好地工作。但是，我尝试将其扩展到1700+ numbers，并得到以下回溯：

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'*

脚本如下：

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)

为什么会发生这种情况，我如何才能让它为那些1700多个数字工作？