Multiple Twitter accounts on iPhone

Hello, I use an iPhone 5 and have 2 twitter accounts. I know how to tweet and manage multiple accounts from the twitter app, but if you want to tweet from Siri or notification centre, does anyone know how to chose which account you tweet from? Both accounts are in Twitter settings, but it will only let me tweet from the first account I added. Any help on how to tweet from a different Twitter account through iOS would be apreciated. Thanks. Callum.