I don't want my girlfriend to continue talking to her ex boyfriend
Why don't you want her talking to her ex?
I personally know how to deal with him and I rather her not be near him.
It's never an easy situation when your significant other is talking to and ex-lover. It's understandable that you're jealous but you shouldn't try to control who they talk to, you should have a discussion with your girlfriend on how you feel about the situation. If you try to just control your girlfriend she could end up leaving you.
You sound like my girlfriend.
I just think talking it out is a better option than trying to control what your girlfriend does.