I'm looking for some help in figuring out the root cause of the issue as explained. While I'm still pretty confused but I think it might be an issue with the mobile service provider. Device: Xiaomi Mi A1 (Android 8.0) It all started a few months ago apparently without a cause. If I kept my mobile data turned off initially for a few hours then I can't turn it back on either from the top-down menu(the icon appears but doesn't turn on data) or from the settings. At the same time if I try to make a call then it'll display "Mobile network not available" although I can see full signal reception. This will be solved(temporarily) if I restarted my device or take the SIM slots out and reinserted them (No - turning off/on Airplane mode doesn't work in this case). If I check in settings --> network --> SIM --> It shows 'CARD 1' (without the Service Provider name). Note: I placed it in Slot 1. I tried SIMs from other service providers and didn't observe any such issue. Tried doing a full factory reset on my device but no luck. Interestingly I happened to observe the same issue with my Lenovo Vibe P1 (Android 6.0). So I figured it could be a problem with my SIM card, so I got a replacement SIM card issued from the service provider retaining the same number. Frustratingly enough I'm getting the same issue back again. I have explained it to the service provider but I guess they might be as confused as I'm. Please see the attached screenshots: (For "Mobile_data_turned_on.jpg" please note that there is still no data/internet connectivity) Any help in determining the root cause for such and possible resolution will be much appreciated..!!