PLS-00221: 'string' is not a procedure or is undefined

We compiled a function which references 7 other functions.
Compilation was successful with no errors. But when we executed the function we got the erorr above. No objects are in invalid status.

Since the user who executed the functions is also the owner of the functions, privilege and synonym are not necessary.

Any ideas what caused the error?

Thanks in advance!

Can you show us how have you called your function? Is it possible that you actually called it like a procedure, not like a function?