Why can't I send texts to a short code?

[AC Question]

I have an LG G5 on a T-Mobile ONE plan. Using the default messaging app, I can't send anything to short codes (e.g. send "IN" to 46787 for a chance to win an NES). First, I get an error, the text message didn't send. Then, if I click retry on the message, it opens a separate conversation with +146787. Then I get a message from 146787 (note, no +) stating "Sorry, this service is not available." I've cleared the app's data, checked the premium sms setting (set to Ask, but the app does not ask when I send to the short code), checked my T-Mobile settings - nothing.

Any ideas?

 

[Rukbat]

Check with TMobile - it sounds like a translation error in their switch.