diff --git a/app/controllers/attempts_controller.rb b/app/controllers/attempts_controller.rb
index dbc5fac1..57576ea5 100644
--- a/app/controllers/attempts_controller.rb
+++ b/app/controllers/attempts_controller.rb
@@ -4,6 +4,14 @@ class AttemptsController < ApplicationController
 
   def twilio
     attempt = Recipient.where(phone: twilio_params['From']).first.attempts.last
+
+    if (twilio_params[:Body].downcase == 'cancel')
+      attempt.recipient.update_attributes(opted_out: true)
+      attempt.update_attributes(twilio_details: twilio_params.to_h.to_yaml)
+      render plain: 'Thank you, you have been opted out of these messages and will no longer receive them.'
+      return
+    end
+
     attempt.update_attributes(
       answer_index: twilio_params[:Body].to_i,
       twilio_details: twilio_params.to_h.to_yaml
diff --git a/app/models/attempt.rb b/app/models/attempt.rb
index cfc80f8a..e82eeca6 100644
--- a/app/models/attempt.rb
+++ b/app/models/attempt.rb
@@ -14,18 +14,28 @@ class Attempt < ApplicationRecord
   scope :for_school, -> (school) { joins(:recipient).merge(Recipient.for_school(school)) }
   scope :with_response, -> { where('answer_index is not null or open_response_id is not null')}
 
+  def messages
+    [
+      question.text,
+      "#{question.option1}: Reply 1\n\r#{question.option2}: Reply 2\n\r#{question.option3}: Reply 3\n\r#{question.option4}: Reply 4\n\r#{question.option5}: Reply 5\n\rReply 'cancel' to stop these messages."
+    ]
+  end
+
   def send_message
     twilio_number = ENV['TWILIO_NUMBER']
     client = Twilio::REST::Client.new ENV['TWILIO_ACCOUNT_SID'], ENV['TWILIO_AUTH_TOKEN']
 
-    message = client.messages.create(
-      from: twilio_number,
-      to:   recipient.phone,
-      body: "#{question.text}\n\r#{question.option1}: Reply 1\n\r#{question.option2}: Reply 2\n\r#{question.option3}: Reply 3\n\r#{question.option4}: Reply 4\n\r#{question.option5}: Reply 5"
-    )
+    sids = []
+    messages.each do |message|
+      sids << client.messages.create(
+        from: twilio_number,
+        to:   recipient.phone,
+        body: message
+      ).sid
+    end
 
-    update_attributes(sent_at: Time.new, twilio_sid: message.sid)
-    recipient.update_attributes(phone: client.messages.get(message.sid).to)
+    update_attributes(sent_at: Time.new, twilio_sid: sids.join(','))
+    recipient.update_attributes(phone: client.messages.get(sids.last).to)
   end
 
   def response
diff --git a/spec/controllers/attempts_controller_spec.rb b/spec/controllers/attempts_controller_spec.rb
index b49a9120..6817dc93 100644
--- a/spec/controllers/attempts_controller_spec.rb
+++ b/spec/controllers/attempts_controller_spec.rb
@@ -48,5 +48,24 @@ RSpec.describe AttemptsController, type: :controller do
         expect(response.body).to eq('Thank you!')
       end
     end
+
+    context 'with cancel params' do
+      let(:twilio_attributes) {
+        {'MessageSid' => 'ewuefhwieuhfweiuhfewiuhf','AccountSid' => 'wefiuwhefuwehfuwefinwefw','MessagingServiceSid' => 'efwneufhwuefhweiufhiuewhf','From' => '+11231231234','To' => '2223334444','Body' => 'cAnCel','NumMedia' => '0'}
+      }
+
+      it "updates the last attempt by recipient phone number" do
+        post :twilio, params: twilio_attributes
+        attempt.reload
+        expect(attempt.answer_index).to be_nil
+        expect(attempt.twilio_details).to eq(twilio_attributes.with_indifferent_access.to_yaml)
+        expect(attempt.recipient).to be_opted_out
+      end
+
+      it "sends back a message" do
+        post :twilio, params: twilio_attributes
+        expect(response.body).to eq('Thank you, you have been opted out of these messages and will no longer receive them.')
+      end
+    end
   end
 end
diff --git a/spec/models/attempt_spec.rb b/spec/models/attempt_spec.rb
index f902ff58..d76158cb 100644
--- a/spec/models/attempt_spec.rb
+++ b/spec/models/attempt_spec.rb
@@ -92,8 +92,9 @@ RSpec.describe Attempt, type: :model do
     end
 
     it 'should contact the Twilio API' do
-      expect(FakeSMS.messages.length).to eq(1)
-      expect(FakeSMS.messages.first.body).to eq("Question 0:1\n\rOption 0:1 A: Reply 1\n\rOption 0:1 B: Reply 2\n\rOption 0:1 C: Reply 3\n\rOption 0:1 D: Reply 4\n\rOption 0:1 E: Reply 5")
+      expect(FakeSMS.messages.length).to eq(2)
+      expect(FakeSMS.messages.first.body).to eq("Question 0:1")
+      expect(FakeSMS.messages.last.body).to eq("Option 0:1 A: Reply 1\n\rOption 0:1 B: Reply 2\n\rOption 0:1 C: Reply 3\n\rOption 0:1 D: Reply 4\n\rOption 0:1 E: Reply 5\n\rReply 'cancel' to stop these messages.")
       expect(FakeSMS.messages.first.to).to eq('1111111111')
     end