How to deal with the encoding when sending a letter?

When sending emails come the bugs here are:
Subject: %u0412%u0438%u043D%u0442%u043E%u0432%u044B%u0435 %u043A%u043E%u043C%u043F%u0440%u0435%u0441%u0441%u043E%u0440%u044B
Name: %u0410%u043B%u0435%u043A%u0441%u0430%u043D%u0434%u0440
Phone: 7 (777) 793-04-02
E-mail: petrovaleksandr1992@list.ru
Message: Hi!

javascript sends this:

$.ajax({
 type :'POST', 
 cache : false,
data:form.the serialize()+'&type=send_form',
 url : '/bitrix/templates/Main/ajax/ajax.php',
 success : function(response) {
 form.find('.table_form').html('<div class="thanks">Thank you! Request has been accepted.</div>');
 } 
 });

what form.serialize() already collects this sort of gibberish. How to get around this problem?

by the way somehow the data from the textarea it displays correctly, and the data from input (with Russian letters) does this.