以前送った資料を差し替えさせてくださいって英語でなんて言うの？

This sounds like a mistake. If it is a mistake it is probably better just to admit it. "So sorry, we sent you the wrong file in error. Please ignore that one and we'll send you the correct one immediately. My apologies!"
1. Here you are sending a more up to date file than was originally sent. You ask the receiver to ignore the first file that you sent.
2. Same as 1.

For example:

Dear sir/madam,

Kindly refer to the document/file I sent you on __ (date).

Unfortunately some of the information in the document had to be amended. Attached herewith is the amended document.

Please don't hesitate to contact me if you have any queries.

Kind regards,

Please find updated version of this file attached to this email.
Please disregard the first version of this document, I have sent a revised version
Here is the updated version of this document.

MEANING= all these phrases will be useful and mean roughly the same thing.

You could also say:
Please replace the previous document with this one
Please see revised version
I have sent a revised one, please use this one.
Please disregard earlier version
Please see amended document
See updated doc (short version)

Hope this helps! ^ ^

Please disregard is a polite way of saying that the disregarded object is cancelled, no longer valid, or no longer under consideration. For instance, if one composed business email and then afterward made corrections to it . . . He could say: please disregard the last email I sent you,

Another way of replacing a file is to describe the reasons for replacing it. This allows your audience to understand why he needs a replacement. Hence one could say: I have made adjustments to the file (or I have updated the file) . . . Here is the updated copy.

Make sure that the receiver of your email understands that the file being sent is the correct and updated one and that all other versions must be discarded.

Disregard - 'do not use' or 'throw away'
Updated - 'newer'

If you want someone to use a new file instead of an old one, you can use the word disregard to tell them the older file is not to be used. If you have 'updated' something, you have made a new version of it.

If you have sent this file already, use 'have sent'. If you have not sent it, say 'will send'. This shows that you are going to do it but have not yet.

The word 'last' has the same meaning as 'previous' in this sentence, you can use whichever one you like best!

Hope this helps, good luck!

Here's a simple example: I have attached a revised or updated version of the document I sent earlier. Please disregard the previous one and use the revised version.

*Could you please disregard the file that I send. I have attached another one for your attention.
To disregard something means to ignore something. Therefore it means you would like them to ignore the email that you send before.
For your attention means for them to look at or consider.

'updated version' means a newer or updated version.
'replace' to put in a new one instead of the one that is there.

We can use the following words to explain that we want to send something else instead:
In place of
Replace

Sometimes we may forget to add in some important or minor details in a file we are sending to someone and we would like to amend it and send once again.
We can use the word 'resend' to show that we are sending again,
"Please accept the email I am resending."
"I am resending the email with a different file attached."

Amend: make small changes
Minor: small