how to call a stored function from another stored function? even possible?

I have a stored functionA that returns void

Inside there I have a line that says:
select functionB();

and it gives this error.

ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function "functionA" line 13 at SQL statement

********** Error **********

any ideas?