12200: Schema validation warning

The provided XML does not conform to the Twilio Markup XML schema. Please refer to the specific error and correct the problem.

• Misspelled verbs
• Incorrect case for verbs; TwiML is case-sensitive, so <Say> works, but <say> will not
• Misspelled or unknown attributes
• Unknown or unexpected nested elements.

• Check the line and column reported by the warning to see what part of your XML response caused the complaint
• Verify that your application server is accepting and properly responding to any custom parameters you may be passing