I would never use WhatsApp for whoring anyway. I find my old dumb retro Nokia is fine, and the only limitation is the amount of text messages it can store. However, I'm pretty ruthless when it comes to deleting them, and only keep very dodgy ones for reference.
I've got a third, secret squirrel phone (smart) for an anonymous Twitter account for a completely different interest, and I've actually installed ClientEye on that, just to check the odd number. My personal phone is completely unlinked to anything escort related.