where is the problem with this sms example?

hi, I'm try out app inventor2, and this is currently an app that I'm testing. the interface look like this. It is a simple app that the user input some text. and key in a phone number which he or she send the text. in other words, it is a sms app.

the block code look like this. when i try to send  a text, it show me run time error. I'm using note 3. and I'm from Singapore, so Google voice don''t work in my country. can anyone able to tell me where is the mistake that i have make. Thanks.