There have been times when I wished there had been a recording of a phone conversation in which I had participated. These have been rare occasions. Yet, it happens.
California law requires consent of the recorded party during a phone conversation. It is easy to inform the other party that a phone call is being recorded. If they object I would state that if it is unacceptable then simply hang up. I would explain that their failure to hang up will be viewed as their willingness to be recorded.
"He said, she said" issues come down to hearsay. A recorded conversation is rather direct evidence. That is why open consent is important.
The above device is the "Mini Telephone Recorder Pro." It can be had for under $80. There are cheaper units on the market. However, the "Mini" saves a call as an MP3 file with date & time stamp. It uses a SD card which offers portability when that becomes necessary.
Do you record your phone calls? Or, do you wish that you could?