Please follow these steps in order to import your CSV file into your Comcast account:
Visit the contacts import portal: https://import.xfinity.com/
On the contacts import portal, click the “File” button.
Click “Browse…” or “Choose File” and select the csv file from your computer.
Click the blue “Import my contacts” button.
Enter your current Comcast email address and password in the Comcast authorization pop-up (if you see one) and click “Sign in”.
Wait a few minutes for the website to show a confirmation message (like “47 contacts successfully imported into your account”).
Please let me know if you were able to import your contacts with all the information you wanted.
Yes, please rename the column “Business Phone”, start the import again and let me know if that solves the issue.
The import should only add the telephone numbers to the existing contacts and should not create duplicates. Nevertheless, if for any reason it creates duplicates you can order your Contacts by their day of creation, eliminate the new ones and re-start the import.
Please let me know if this helps and you are able to solve the issue.