Data-pla-only not working on android?
I thought I'd just share one little piece of knowledge I just found.
I have subscribed to a second SIM card, tight to my main one.
(The name of this option with my carrier is SFR Multisurf).
With this "data-only" SIM card, one needs to use a specific APN (named websfr).
Unfortunately, this APN is set by default to have the "dun" type only, at least on my SGS2/4.1.2.
With a "dun" type APN, one can't use the Android device as a real Internet/Data endpoint. Dun stands for "Dial-Up Networking" and is made to use your device as a modem only.
Changing the APN type to "default" (or even "default,supl,dun") is enough for the APN to become a working access point to the Internet.
To do so, you have to go into your Phone/Tablet settings, then Select More, then Select Mobile Networks, then Select Access Point Names.
Find the access point you need to use, scroll down to its type, make sure it is set to "default" and voilą !