# Download the twilio-ruby library from twilio.com/docs/libraries/ruby
require 'twilio-ruby'
require 'sinatra'

get '/sms-quickstart' do
  twiml = Twilio::TwiML::MessagingResponse.new do |r|
    r.message(body: 'Ahoy! Thanks so much for your message.')
  end

  twiml.to_s
end

# Download the twilio-ruby library from twilio.com/docs/libraries/ruby
require 'twilio-ruby'
require 'sinatra'

post '/sms-quickstart' do
  twiml = Twilio::TwiML::MessagingResponse.new do |r|
    r.message(body: 'Ahoy! Thanks so much for your message.')
  end

  twiml.to_s
end

Change from get to post (Twilio's default method)
Change from get to post (Twilio's default method)