I have 250MB data on my phone for emergency use, why recently every time when I turn on it not work?

[porcupine]

Also is your data turned on 

[hTideGnow]

hi @Li777 

did you login My Account and confirm if it shows you have the 250Mb data no used?

and what phone do you have?  Data problem could be related with APN.   Please  Reboot phone and then Reset network Settings and test again