Is this possible with this situation?

So the parent account is a checking account (not a credit card account)...and out of that checking account, they got a credit card which is a subaccount to that checking account.  At least this is how the owner described it to me.  

He said he has tried to link the credit card but it seems to be impossible to do it without also linking the checking account.  We only want the credit card to be linked and not the checking account.