how to name photos in iphone????

Quite new to the whole iphone thing so please be kind. I have taken some pictures with the iphone for work which needs to be emailed. i have to rename the file name to a specific name so that the mailbox at work will send it to the correct drive/folder at head office. I can't seem to figure out how to change the pictures filename from within the iphone as i don't have facility to connect to a laptop to do it. Please could anyone help me with this either by the use of an app or some other way on the iphone.
Thank you for your help
stu