Why can't I change the data cap on my phone?

[AC Question]

I have a Samsung Galaxy A5 2016 (SM-510F) running Android 7.0 and I cannot change the data cap. I used to be able to change the data cap and the bill cycle but I simply cannot anymore, there is no button to do so and the option to change the data cap is greyed out. Back when I was able to change it, I set it to 2GB, but because I get a new data plan, I need to increase it.

 

[Tim1954]

Have you got mobile data monitoring On?

 

[Rokas Kazlauskas]

OP here, only created an account now. Silly me, I didn't know that mobile data has to be ON before you can change the data limit. I swear i tried this before, maybe I just didn't notice it.