Just be aware that even if you are technically capable of recording a phone call it may not be legal for you to do so.
There are significant, overlapping Federal, State and even foreign laws that define the circumstances in which you can legally record a phone call. If you haven't met the consent requirements on a call you can be subject to criminal and civil penalties; and in some states it's a felony.
In most cases it's best to play it safe by notifying all parties at the beginning of your call and obtaining their clearly stated consent as part of your recording at the beginning of the call.
Here are a couple of sites that provide additional, detailed information:
Justia
Digital Media Law Project