<%= f.fields_for :billing_information, @customer.billing_information do |b| %>
<%= render partial: "billing_information/form", locals: { info: @customer, b: b } %>
<% end %>
<%= f.fields_for :contact, @customer.contact do |b| %>
<%= render partial: "contacts/form", locals: { info: @customer, c: b } %>
<% end %>