Send data from a check label

Good day, I've the following problem, I'm making a form that I sent the data to a Gmail email, the problem is that when choosing a plan, the page throws an error. The mail arrives without any inconvenience and the selected plan but, the page remains with the error. Here I take the data and organize it to be prepared to be sent to Gmail. I'm using the PHPMailer library

$mail->Body = "<h3>Nombre : $nombre <br>Empresa : $empresa <br>Direccion : $direccion 
    <br>Contacto: $contacto <br>Email: $email <br>Ciudad : $ciudad 
    <br>PlanA : $planA <br>PlanB : $planB <br>PlanC : $planC <br>PlanD : $planD </h3>";

This is the error that marks the page

And This is what I have in the HTML part

When sending them, the error on the page jumps. Is there any way to fix it?

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