Extra time spent looking for the

[mijanbokul]

It's difficult to closeThe pop-up should have a clearly visible button to close it. "cross" will only irritate the user. To get rid of the intrusive form, he can completely close the tab (or even open the competitor's site). A

well-designed pop-up will not be hindered by a noticeable button from collecting clients.
Not adaptable to smartphones
Take care of users who open the site from a smartphone. A pop-up window whatsapp number list that spreads across the page is unlikely to collect many contacts. It will simply require entering data.

Adapt the form, and people will only thank you.
Interrupt the target action
Don't prevent the user from completing the action for which he came to the site - the pop-up will confuse him. And then he will not complete either of the two tasks.

Track the user's actions and show the pop-up at the moment when the person is interested - not immediately and not when he is already buying something.