index.html

<!DOCTYPE html>
<html lang="pt-BR">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <link rel="stylesheet" href="style.css">
    <title>formulario</title>
</head>
<body>
    <div id="container">
        <form id="enviarForm">
            <label for="Nome">Nome</label>
            <input type="text" id="nome" placeholder="Digite seu nome" required>

            <label for="email">Email</label>
            <input type="email" id="email" placeholder="Digite seu email" required>

            <label for="Telefone">Telefone</label>
            <input type="tel" id="telefone" placeholder="(00) 00000-0000">

            <label for="assunto">Assunto</label>
            <select id="assunto">
                <option disabled selected>Escolha um assunto</option>
                <option>Abrir um chamado</option>
                <option>Emissão de 2° via</option>
                <option>Ouvidoria</option>
            </select>

            <label for="mensagem">mensagem</label>
            <textarea id="mensagem"></textarea>

            <button type="submit"><span>Enviar</span></button>

        </form>
    </div>
    <script>
        enviarForm.onsubmit = function(){
            event.preventDefault();
            window.location.href = `https://api.whatsapp.com/send?phone=5585987985414&text=ol%C3%A1%20me%20chamo%20${nome.value},%20meu%20email%20%C3%A9%20${email.value},%20meu%20telefone%20%C3%A9%20${telefone.value},%20e%20quero%20falar%20sobre%20${assunto.value},%20${mensagem.value}`;
        }
    </script>
</body>
</html>