In order to set up an Auto-Response in Twilio you will need to log into your Twilio account at https://www.twilio.com/
Go to Twilio's Studio
This will bring up the Dashboard. Click on the Create a flow button
Give your flow a name. I've named mine Auto-Responder here. Hit the Next Button.
Scroll down until you find the Message Auto Responder box. Select the box and hit the next button. This will bring you into the Studio to edit your flow.
Click on the send_message box in the center to edit the message.
This will pop up an edit box on the right. Under the Config tab I will make mine say "Thank You for responding. If you have any questions please call us (603)-298-5721." Click on the save button and you will see your message within the send_message box.
Next click on the Transition tab within the edit box. As this is designed out of the box, if a message fails to send it will just stop, it won't try again. In order to make it repeat until successfully sent you will need to tell it to do that under If Failed to Send by clicking on send_message under Existing Widgets.
Click on Save and you will see the work flow loops back to send_message now.
Click on the Publish button, a pop up will appear. Click on the publish button again. And you've built your first Flow.
Now you have to link that flow to the phone number you have coming out of store.
Below Studio on the left hand nav bar inside twilio.com is the Phone Numbers tab
Click on the # tab. You will now see your active numbers. Each number is in blue as a hyperlink. Click on the number you want to add the auto response to.
This will bring you to the properties for that number. Scroll down to the bottom where there's a Messaging header
Under the line A Message Comes In the first drop down should be set to STUDIO FLOW the second box you will set to the name of the flow you just created. Mine is Auto-Responder. Click on the Save button below.
My messaging section now looks like.
Next step is to test this from with iM. Send yourself a text message (Interfaces > Twilio > Send to Phone Number), reply to it and if everything was set properly you will see your custom auto-reply.