Hmm , well I remember me & a bunch of my buddies decided to play this prank on one of my friends , and we used an app called SpoofCard to change our phone number & disguise our voice when we called .. We then found out after that you can record the calls . It's not free , but it's reasonably priced .
Google Voice also has a feature like this ; but this might or might not matter to you ; but to record , the person has to make the call to you , & it clearly states over the line that conversation is being recorded .
I haven't used Google Voice in a while , so don't kill me if my information is out-dated .