Backbone can't uncheck the checkbox

I have a form with some field, and there is a special checkbox which shows only when a client has certain IP address. The problem is that I can't uncheck the input even though there is an event bind to it. Here is some code: HTML

{if $rhOptions==1}
  <label class"label">
    <span class="label-name">Tel order:</span>
    <input type="checkbox" name="zamow_tel" {if $user.zamow_tel}checked{/if}>
  </label>
{/if}

JS

UserView.prototype.events = {
      'keyup :input': 'silentSave',
      'submit form': 'submit',
      **'change input:checkbox': 'checkbox',**
      'click [data-copy]': 'copy',
      'change [name="type"]': 'type'
    };
UserView.prototype.silentSave = function() {
      var data;
      data = this.$('form').serializeForm();
      return this.model.set(data, {
        silent: true
      });
    };

    UserView.prototype.checkbox = function() {
      this.silentSave();
      return this.render();
    };

For other inputs the view is rerendered. Does anybody know what is wrong? Thx in adnavce