My Twitter has gotten hacked?

Someone has been posting tweets on my twitter since last night. I have deleted the unwanted tweets and changed my password, and about an hour ago more tweets popped up. I think they are on a mobile device because I had to revoke access from my account from twitter for android (I have an iphone). What do I do about someone who has hacked my account from a mobile device?

Contact twitter maybe they can block that number/mobile device from accessing your account. And block any people if you can