Recording a Phone call

How to Record a Phonecall using Arduino NANO ? Can anyone send me the code

No.

Perhaps a very short phone call - 2k of SRAM is not going to hold more than a fraction of a second speech sampled at 8kSPS!

Add an external RAM chip or SDcard to the equation, things become more plausible.

As for the code, that depends on what hardware is used. Have you looked for existing projects for recording/playback?