The problem is this:
Once the form is filled out and the send button is clicked, the button allows you to click it several times, which causes the same message to be sent several times, for example, if someone clicks on the button 5 times, 5 repeated messages arrive.
The correct operation should be that, when you click on the submit button, it does not allow any more clicks, until the form has been submitted.
If you want to try the form, you will see that it lets you click the submit button several times.
I will be attentive to your answer.
Thanks,
Marcos.