Can Google Hangouts send out text message under data? I found that on my android, google hangouts seems not able to send out text messages i.e. SMS to a phone number, when it is on data service. 

Is it the same for others, or is it just my problem?

Thanks.
You can send text messages through hangouts to phone number. For this You have to go to Settings &gt; Messages &gt; Default messaging app &gt; Hangouts.