My cron doesn't find a file

I have written a Python script that I would like to run by crontab! I have run the Python script individually and it works fine! The problem is that when I run it by Crontab, I receive an error indicating that one of the Python files that it called does not exist.

The error in /tmp/listener.log is as follows:

Traceback (most recent call last):
  File "/root/telegram/sendmsg.py", line 21, in <module> 
  file = open("List.csv") 
FileNotFoundError: [Errno 2] No such file or directory: 'List.csv'

Despite the fact that my file exists and it runs when I run my script without crontab!

I have my crontab set up like this:

30 14 * * * /usr/bin/python3 /root/tele/msg.py > /tmp/listener.log 2>&1

My Code:

import csv
from datetime import date
from timeIR import *
from persiantools.jdatetime import JalaliDate
from persiantools import characters, digits
import requests

def send_to_telegram(message):

    apiToken = '****'
    chatID = '***'
    apiURL = f'https://api.telegram.org/bot{apiToken}/sendMessage'

    try:
        response = requests.post(apiURL, json={'chat_id': chatID, 'text': message })
        print(response.text)

    except Exception as e:
        print(e)

file = open("List.csv")
data = csv.reader(file)
data = csv.reader(file, delimiter=",")

whoisinshift = []
shiftname = []
phone = []

today=digits.fa_to_en(ShowDateDay())

for row in data:
    listdate = row[0]
    if listdate==today:
        mydate=digits.fa_to_en((ShowTodayFull()))
        whois=row[1]
        phonenumber=row[2]
file.close()

mymsg=u"\U0001F4C5"+"\t"+mydate+"\n"+u"\uE13B"+"\t"+whois+"\n"+u"\U0001F4F1"+"\t"+phonenumber
send_to_telegram(mymsg)