Automatically Link Contacts to Accounts

I have imported all my Accounts and Contacts into Zoho CRM. I have 3000 accounts and 11000 contacts. Unfortunately the link from contact to account did not happen.

From what I can see, all I need to do is populate the Account Name field of the contact with the Account Name of the Account. If I do this manually then I see the contact associated with the Account in the Account record.

Anyone know how to write a custom function to do this automatically based on the main phone number as the contacts and account have the same phone number.