Unable to receive USSD sessions while iPhone 5s screen is locked While my iPhone's screen is locked, I am not able to receive any USSD session on it. There is no notification of it as well. If I keep my screen on I receive it fine.

Is this a phone restriction or some network problem?
USSD session messages no longer turn on the screen. This was intended to save battery.  

I for once had a problem that the USSD message would arrive when the iPhone was in my pocket and the screen would be ON until I manually dismissed it, which would drain my battery.