Macro to check against Columns & Delete Duplicates

I have an excel spreadsheet that has 4 columns of phone number. The first 3 are Home Phone, Cell Phone, Other Phone. The 4th column are phone numbers from a phone hotline of people that called in. I want to check the 4th column (numbers of people who had called in to the hotline) against the other 3 columns for duplicates. If the phone number already exists in the first 3 columns, the number in the 4th column (ONLY) should be deleted. The phone number format for the first 3 columns are (999) 999-9999. The phone number format for the 4th column is 999-999-9999.

Someone was nice enough to send me this macro quite awhile ago, (I don't remember who to thank them) but it doesn't seem to be working. It is not erasing the duplicates. Can anyone please advise?

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