Record Conversations on your iPhone
Yes you can. If you want to do this, it's quite easy and simple to do, and you can transfer them to your mac later with a 3.5mm headphone cable. First, you may want to give it a whirl by calling a friend, or a 1800 number to see if you can do it without forgetting how to use your iphone, because you'll need to know what to do in an instant if something goes awry.
Get your headphones or bluetooth headset ready, it makes it way easier, speaker phone on the iPhone just sucks, IMO.
Become familiar with the 3way calling feature and all of it's features during a call (practice once or twice, it's easy)
Then start recording your calls.
I'm lazy, so I didn't want to see how long you can record a conversation on this system, but I imagine it's not very long, but with some simple social engineering, you can just rinse and repeat as much as you need to during your recorded call.
So, what you do is make your call. As soon as you are able to make another call (maybe add your phone number to the top of your contact list for ease of dialing, or just dial it like i do, cuz' I'm fast like that), you make the call (no pun intended) when to do this since the person may pick up immediately and then hang up if you are slow, or if it's a 1800 number you'll have plenty of time to prep the other line. CALL YOURSELF, you'll hear your lovely voice come on the line stating you are away or whatever, HIT THE "#" key, you'll hear a tone, now your are recording! MERGE THE CALL! If you are calling a company start going through the process of hitting "1" for english etc. If you are calling a friend or victim, just wait for them to pick up the line and viola, you're recording! I'm not sure how long this will last, but I don't care. If I did, I'd test it out and see how long I could record a message, take not of the time and simply keep a timer running while i was talking to the person (built in stopwatch on the iPhone maybe?! just give yourself a buffer! You don't want the nice lady from AT&T to come on the line while you are recording to spoil the whole recording etc. "If you are satisfied with your message, press 1 now...." you get the idea...) If you need more time then voicemail will give you, simply ask the person you are calling if they could hold on for just a second, no need to even give them a reason, they'll usually just say, sure. Go to private mode with your voicemail, hit the "#" key, then the "1" key 2x to send it to your voice mail, then restart the whole process over again and wait for the tone, and record part 2 of the conversation! You can hang up on voicemail while keeping them on hold, etc. so there is no need to panic, just start another call, and repeat the steps above and keep recording. You might even be able to stop and start a new recording if you are calling a company and they put you on hold. I find that these are perfect times to put THEM on hold and start a new recording. Easy! Takes some practice, but I have no problem doing it. Be aware that if you don't tell them you are recording them, it maybe illegal to record them. That decision is up to you.
Then all you have to do is transfer them to the computer (unfortunately in realtime, but maybe someone will know how to get them over maybe from a backup of the iphone files when the phone backs itself up. I seems like they backup the voicemail too because when I got my new 3G the voicemail came along with it, not sure if it was coming from iPhone backup files on the computer or from AT&T).
Good luck!