Why does my phone say I am roaming when connected to my "home" network?

Question

I recently got a new phone, the Elephone P7000 and it runs stock android 5.0. Everything seems to work perfectly apart from the fact that most of the time the top status bar says I am roaming.
When I check which network I am connected to, it says I am connected to my actual provider network, so why does it say I'm roaming. The only partial fix to this issue is manually selecting the cellular network, and this only works for around 10 minutes with no roaming shown in the status bar, after that it switches (? – I don't know if it actually does since I still seem to be connected to the same network) by itself when I am not moving and I get the roaming indication again.
So far, this does not seem to affect my ability to make calls or receive messages, but I find the roaming indicator in the status bar to be very unsettling.

Edit to clarify:
On my network operator selection screen, I see the same operator name multiple times and only upon selecting one specific (the topmost) option I get no roaming indication.

Any help or clarification would be appreciated.

Answer 1

Let me guess, you're on EE? Or a network that uses EE for it's coverage? (like Virgin or Asda). These swap between the Orange and T-mobile masts depending on which has the strongest signal, and when that happens the phone thinks it's then "roaming".

When you see 2 versions of the same network operator, you'll often see different capitalisation, e.g. "virgin" and "Virgin". One of these is actually Orange and the other is T-Mobile.

It doesn't have any negative effects.

Answer 2

Internally, mobile networks identify themselves through a Mobile Country Code (MCC) and a Mobile Network Code (MNC). The MCC and MNC of "your" network are stored on your SIM, along with other data with which your phone identifies itself to the carrier.

Each cell tower transmits a cell ID, which also contains the MCC and MNC. When you are connected to a mast whose MCC/MNC pair differs from that on your SIM, the phone assumes you are roaming on a different network. This is usually the case when you are traveling abroad, but there is also "national roaming" (the MCC is the same but MNCs differ).

However, some carriers have multiple MNCs within the same country. US carriers have a handful of MNCs. In Europe this is less common, but occasionally mergers between carriers have resulted in multiple MNCs being assigned to the same carrier.

Edit: I recently saw a portion of the Android source code which has lists of which networks are not considered “roaming” for a SIM issued by a particular carrier. Thus, if you are running a recent version of Android and you’re on a network which uses multiple MCC/MNC pairs, Android will not show the roaming icon. However, this will only work if your phone runs a version of Android which already “knows” about these MCC/MNC pairs being part of the same network. If it doesn’t, Android will mistakenly report your status as roaming.