Lost (possibly stolen) iPod Touch 4th gen. Any way to sever its ties to my account and other devices?

I need a way of severing all services (such as message receiving and connecting to my iPhone texts) from my iPod Touch 4th gen remotely as I'm concerned it has been taken and I did not activate 'find my iPod' before its disappearance. I have already changed my Apple ID passwords in the hope that it would require my new password to recieve any further messages. I tested it on my iPad and this is seemingly not the case. I also do not want whoever has it to be able to see my mobile conversations as I also own an iPhone and I do not want them to be able to recieve all messages sent to and from my iPhone. Basically I just want to make it so no one can use any services using my account.