A few months ago I found an application in F-Droid that according to the description allowed to record phone calls in android phones so I downloaded it, it started but when tried to record a call for testing i got an error and it stopped working. After that deception I thought “it is an open source application (due to F-Droid is a repository of open source applications, you should check it out) I could download the code and check if I can help”.