How much control does a lender have over borrower's credit score?

Here's the thing:

If a company buys a note from a bank, thus, becoming the lender to the original borrower, how much control does it have over borrower's credit score?

If the new company assumed the mortgage, can it change/remove any of the notes on the credit score of a borrower? Meaning those that were made the original lender.

I'd really appreciate answers. Thanks a lot!

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