Oracle 存储过程怎么执行

写了这么一个存储过程:
create or replace procedure simpleprocedure(v_id in number, v_name  out varchar) is
begin
  select name into v_name from student where id=v_id;

end simpleprocedure;调用:
declare
v_id number:=5;
v_name varchar2(100);
begin
v_name:=simpleprocedure(v_id,v_name);
dbms_output.put_line(v_name);
end;报错:PLS-00222:在此范围中不存在名为'SIMPLEPROCEDURE'的函数
     PL/SQL:sTATEMENT IGNORED
请问错在哪里啊