My e-mail, exchange account, on iphone, displays an out of date signature. My Outlook displays the correct signature but this does not appear to have replicated to my iphone.

My e-mail, exchange account, on iphone, displays an out of date signature. My Outlook displays the correct signature but this does not appear to have replicated to my iphone. The standard signature still says "sent from my iphone" which is fine but I need desperately to change the exchange signature as the office address is incorrect.