Changing the customer on the project and expecting the newly generated invoices address to have the

We have a project which has a customer A and its been funded properly. After certain activity on the project, we would like to change the customer on the project to Customer B. Lets say previous funding is for $10K with customer A. I did a -$10K funded with the customer A meaning that there is no funding on the project associated with Customer A.

I have created a new agreement with Customer B and funded the $10K to the same project.

I believe this wouldn't work because the customer contribution is 100% on the Customer A and its greyed out. Customer B has 0% contribution on the project even though I have added to the "customer and contacts" on the project.