I've been using "Call Recorder" by Skvalex since I got my first android. https://play.google.com/store/apps/details?id=com.skvalex.callrecorder To be effective some of the call recording apps need Root + kernel support for direct recording (Best quality), Otherwise they record from the microphone & earpiece (acceptable if a bit noisy). My memory is not great at the best of times and this app has been a godsend. Also it's great to tell those Spam marketing callers that you are recording the call for security proposes (the tend to hang up when I say this for some reason...) ^_^