Click-to-WhatsApp ads are good at one thing: getting a buyer to open a chat. The message that arrives is often the pre-filled one, "Hi, I'm interested", with no model, no city and no budget. Someone on your team has to reply "which car?" and hope the buyer is still there.
Ads run in the evenings and over weekends, when the showroom is closed, so the leads you paid for queue up until morning. Meta also gives you a head start you can waste: when a buyer starts a chat from one of these ads and you answer within 24 hours, Meta opens a free entry point window of 72 hours in which your messages to that buyer are not charged. Reply after 24 hours and that window never opens.
And when the month ends, nobody can say which ad brought buyers and which brought browsers, because the leads were never tied back to the ad that produced them.