Importing and mass correction

Hello, i made an error some time ago while importing and would like to fix this.

So when i update the fields with errors and import it back in it works no problem,

However if i leave fields blank in the excel doc, where there previously had been information, the import doesnt delete it and just leaves whatever information was there before!

Is there a way to remove a bunch of information and return the fields blank ?

For example i only have tax ID on some custommers and have by mistaken applied it to some custommers that i dont have the tax ID for. So now i would like to remove those wrong tax ID’s. Any ideas ?

ok i fixed the tax ID part by simply inputting an X in the fields i wanted to delete.

but then i got sales partners, in which i cant do that xD any way to delete sales partners on some custommers ?