I suggest adding "temporary" fields for email and phone to your contacts (where you have first and last names) table.
Then, after you import the file into contacts, you then need to push the email and phone out to the related tables. Depending on how the tables are setup, you may not even need a script. Do you currently add email addresses and phone numbers by clicking in the empty row of a portal?
Yes I do.
I was mistaken about possibly not needing a script (I was erroneously thinking the "Replace Field Contents..." would add related records), so you do need to write a script:
Go to record/request/page [first]
Set field [ related email field ; temporary email field ]
Set field [ related phone field ; temporary phone field ]
Go to record [ next; exit after last ]
If you're going to do this frequently, you need to improve this because right now, ***if you run this script without first ensuring your found set is the set of imported records, you're going to delete all your existing phone numbers!***
Try running it without the loop first just to make sure it works on the first record.
Backup your database first.
Make sure users can't accidentally run this script (e.g.: make sure it doesn't appear in the scripts menu).
When you're done, if you don't want to delete it, just add "exit script" as the first line to ensure nobody runs this script.
Once it's all done you can delete the temporary fields, or their contents.