When changing the Company Information in the Financial Subpage the following error Message is displayed:
"Company Name or Billing Currency cannot be changed after transactions have been posted."
This is working as expected. To change the Company Name, the financial transactions have to be removed (after all chargeable financial transactions have been invoiced for the existing Company Name).
This will impact existing Cost, Benefit and Budget Plans on the Project i.e. the financial actuals will be removed.
Please test on a test environment before applying on your production data, also backup your data before performing the steps.
Another alternative is to create a new project with the correct Company Name