If I may offer a possible solution, I think the following will work:
First off, here’s a dummy [People]
table I mocked up with names, emails, and partially-filled phone numbers:

Export the Excel data as a .csv, then import that into a new table in Airtable. I’ll call this [Email2Phone]
. Make sure the email addresses are in the primary field, as this will associate each email with the proper phone number. Here’s a quick mockup table I made with that in mind. Notice that the emails and numbers are not in the same order as in my existing table:

Back in your existing table ([People]
in my sample), change the field type of the current email field to a Link, and point it at the [Email2Phone]
table. This should keep the existing data, but just change everything from literal text to links to the associated records from the [Email2Phone]
table:

Looking in the [Email2Phone]
table, there should now be a {People}
field that looks something like this:

Back in [People]
, change the {Phone}
field to a lookup, using the {Email}
links to pull the related phone numbers from the [Email2Phone]
table:

That will populate the phone number field with all of the phone numbers matching the linked emails.

Now just reverse the last two steps. Change the {Phone}
field back to the phone type, then change the {Email}
field back to the email type. In both cases, Airtable will retain the data, so you’re left with this:

You can now remove the [Email2Phone]
table, as it’s no longer needed.