Iphone texts received on 2 phones?

I updated my iphone 4 to the latest ios software on itunes and now when i text people and they reply, it shows up on my dad's phone! How can i change this so when i send and receive texts, it's only on my phone?
It shows the texts i send and what they reply on both of our phones!

I'm going to assume that your dad owns an iPhone as well.

It is most likely an issue with iMessage. One is registered with an email, and then you have a phone number registered along with that email. Both phones are registered as iMessage devices on the same account. So turn iMessage off on his and you should be ok.

If not… Well, I don't know what to tell you.