Loan Units Are Not Working Correctly

[Digital Phoenix]

So I gave received some loan units from my other DS. I click on "Use Loans," I click on the file I want, and then I click on the loan characters I want to use... After I'm done, I click B to back out since there's no other way to do it. I try the single player campaign, and it doesn't work. I try the online, and it doesn't work. What am I doing wrong exactly?

Edit: Never mind, I figured it out. You can only use one loan unit.