Still receiving txts from the person before me's iPhone i bought

I recently bought an iPhone 4 from somebody off Craigslist and have been receiving their texts. The phone is off but can sometimes still text so I have been texting time to time on it but I guess whoever had that number still can text from it but why am I receiving their texts still? Its so annoying! Like is there anyway to stop it? I'm getting it flashed to cricket this weekend probably so maybe they can give me a new number? I just wanna know if anyone else has experienced this?

I had the same problem, just tell the people who are texting you that your not the person they are looking for.

You should have had the number changed immediately. He would have kept his same number, but you couldn't keep that number. Make sure you change it.