You have to be careful recording phone conversation without their permission, especially if you are going to publicity post the recordings. As long as you stated to them before starting the conversation that you are recording the call, you are off the hook.
If you don't do this, you are liable to get sue.
Why do you think all CIC calls usually start by saying calls are recorded? This is to protect agents from abusive callers. So since they stated that they are recording it, you must also state that you are also recording it as well to protect yourself from CIC abuse.