_phone.html.erb

<fieldset>
<div class="control-group">
  <%= f.label :place, :class => "remember control-label" %>
  <div class="controls">
  <%= f.select :place, ['Work', 'Mobile', 'Other'], {}, { :class => "input-xlarge" } %>
</div>
</div>
<div class="control-group">
  <%= f.label :number, :class => "control-label" %>
   <div class="controls">
  <%= f.text_field :number, size: '20', :class => "input-width field-clear" %>
</div>
</div>

<div class="control-group">
  <%= f.label :email, :class => "control-label" %>
   <div class="controls">
  <%= f.text_field :email, size: '20', :class => "input-width field-clear" %>
</div>
</div>

  <a href="#" class="remove" data-confirm="Are you sure?">remove</a>

  <%= f.hidden_field :id %>
  <%= f.hidden_field :_destroy %>

</fieldset>

contact.rb

class Contact < ActiveRecord::Base
  attr_accessible :background, :bcard, :company_id, :first_name, :last_name, :linked_in, :user_id, :phone_numbers_attributes
  belongs_to :company
  belongs_to :user
  has_many :tasks
  accepts_nested_attributes_for :company
  has_many :phone_numbers
  accepts_nested_attributes_for :phone_numbers, allow_destroy: true
  mount_uploader :bcard, FileUploader 

index.html.erb

		<div class="items">
			<a href="#" class="add">add phone</a>
			<%= f.nested_fields_for :phone_numbers do |f|
				render 'companies/phone', f: f
				end %> 
			</div>

output log on POST

Started POST "/contacts" for 127.0.0.1 at 2013-09-02 14:50:04 +0300
Processing by ContactsController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"Nhflt/o9HdfsWXpsSaKddd5yvItOsGtDoFD5N/Rbfns=", "contact"=>{"first_name"=>"esdzxc", "last_name"=>"", "company_id"=>"1", "phone_numbers_attributes"=>{"1378122596463"=>{"place"=>"Work", "number"=>"1234", "email"=>"awds", "id"=>"", "_destroy"=>"false"}}, "linked_in"=>"", "background"=>""}, "commit"=>"Add Contact"}
  Company Load (0.2ms)  SELECT "companies".* FROM "companies" WHERE "companies"."id" = 1 LIMIT 1
   (0.1ms)  begin transaction
  SQL (348.7ms)  INSERT INTO "contacts" ("background", "bcard", "company_id", "created_at", "email", "first_name", "last_name", "linked_in", "updated_at", "user_id") VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)  [["background", ""], ["bcard", nil], ["company_id", 1], ["created_at", Mon, 02 Sep 2013 11:50:04 UTC +00:00], ["email", nil], ["first_name", "esdzxc"], ["last_name", ""], ["linked_in", ""], ["updated_at", Mon, 02 Sep 2013 11:50:04 UTC +00:00], ["user_id", nil]]
  SQL (0.3ms)  INSERT INTO "phone_numbers" ("company_id", "contact_id", "created_at", "email", "number", "place", "updated_at") VALUES (?, ?, ?, ?, ?, ?, ?)  [["company_id", nil], ["contact_id", 8], ["created_at", Mon, 02 Sep 2013 11:50:04 UTC +00:00], ["email", "awds"], ["number", "1234"], ["place", "Work"], ["updated_at", Mon, 02 Sep 2013 11:50:04 UTC +00:00]]
   (166.7ms)  commit transaction
  Rendered contacts/_contact_card.html.erb (0.8ms)
  Rendered contacts/_contact_info.html.erb (1.0ms)
  Rendered contacts/create.js.erb (3.8ms)
Completed 200 OK in 601ms (Views: 38.4ms | ActiveRecord: 516.0ms)

phone_number.rb

class PhoneNumber < ActiveRecord::Base
  attr_accessible :company_id, :contact_id, :place, :number, :email
  belongs_to :company
  belongs_to :contact
end