What is this text message, and how worried should I be? The following text message popped up on my iPhone, and it doesn't seem to be coming from the Message app or any other apps on the phone. Obviously this is a spam. But which app is showing this message, and how worried should I be?

(I am listening to a podcast in Downcast app when the message appeared.)
Note: The previous answer is wrong. Correct answer is the message is from the service provider. Thanks to @duci9y for the correction.