The credit reporting company maintains the report
Equifax, Experian, and TransUnion receive information from furnishers and assemble consumer reports. A bureau dispute identifies the item in that report and asks the reporting company to investigate.
The furnisher supplied the account information
A lender, card issuer, collector, or other business may be the furnisher. A direct dispute generally should use the address designated for disputes and include sufficient account identification, the specific information disputed, the basis, and supporting documents.
Some direct disputes have exceptions
Current Regulation V lists exceptions involving certain identity details, inquiries, public records, fraud alerts, and information supplied by another furnisher. Read the current regulation rather than assuming every issue should be sent to every recipient.
Official sources
Review the current government sources before acting because requirements and contact information can change.
CFPB: How to dispute an error Regulation V § 1022.43