I'm currently on a vacation with a new phone who worked perfectly on the country I bought it at (SMS, calls, data...) but now, when im abroad, the data wont work although I can make calls alright. But if I try to change the APN's MCC and MNC codes which currently is set to Belgium for some reason (I'm currently in Germany) to something other than the default ones, it just removes the APN entry from the APNs list.
What can I do to change the APN's MCC and MNC codes? Are there any reason that they would be locked or something similar?
I have a Nexus 5 Android KitKat 4.4.4