Why the cellular data network does not work?

[CliffWu]

Sometimes, I only have cellular service , but not LTE data service? why is this? and It really bothers me a lot?

Could you please let me know why 

[Phil_Adelphus]

@CliffWu   Have you tried rebooting the phone and/or turning airplane mode on for a few minutes and then off again?  If it still doesn't work you might want to submit a ticket at the chat icon bottom right of this page.   You couldn't have set a data limit in the phone settings by chance?

[CliffWu]

Yes, only voice service, no data! (my subscription includes 10GB data, my usage not even  reaching 1Gb for the month). The LTE indicator is not showing if my phone is out of WIFI. I have not modified my cellular or WIFI settings for a while. Not sure what's going on.

[Phil_Adelphus]

@CliffWu    Do you mean your phone works for voice calls but not data?  Does the phone drop from LTE to 3G when you make a phone call?