Adding WhatsApp to the site does not by itself bring customers. The button is not a sales process. The click should be countable, and the person who replies should be named. If nobody replies, the button is a door nobody watches.
What the button solves, and what it does not
The button makes writing easier. It does not ask the job, the quantity or the timing on its own. The form carries that detail. WhatsApp is not an excuse to hide the form. Both can sit on the page. Neither replaces the other. With only the button, sales has to pull a job out of a scattered chat.
The click should be countable
A click that is not counted is absent from the report. If a person from an ad and a person from the site hit the same button, the two should be told apart. If they are not, you cannot know which door is doing the work. The count sits in the company ads property. A number on a supplier personal screen is not your record. A position is not tied to that number.
The person who replies is named
The number the button opens belongs to a person or a rota. The number is a company line, not a private phone. If that person leaves and the line closes, the enquiries close with it. Who looks outside working hours is written down. If it is not, the button stays open at night and the reply is unclear in the morning. The first reply asks for the job, the quantity and the timing. A greeting is not an enquiry.
The accounts stay with the company
The company should own the domain, the ad account, and the code. If the button is a script the supplier pasted and the code is not yours, you cannot change the counter. HED Creative, the partner in Berlin or Ankara, adds the button only when the person who replies is named. If nobody is named, the form and the inbox come first. The button comes after.
To have the setup written, say on website development who owns the number. If ads must count the same click, the Google Ads agency uses the same event. The count table: company site measurement plan.