1. Zogundar's Avatar
    Still running Android 4.4.2, with a T-Mobile phone.

    With mobile data off, calls fail to connect at all. With it on, they connect immediately.

    I first had an issue last month and at the time I "fixed" it by resetting the network under Settings/More Networks/Mobile Networks/Network operators. Now the only two numbers that will "work" are ones placed to another phone in the house and T-mobile. And the latter dropped on me.

    After I tried again with another phone, T-mobile wanted me to do a factory reset. -_-

    I also managed to place a call via Wi-Fi calling, but that's not really an option outside the home and has never been terribly reliable in the past.
    03-05-2018 06:34 PM
  2. B. Diddy's Avatar
    Go to Settings>Mobile Networks>Preferred Network Type. Is it set to 4G LTE only?
    03-06-2018 01:02 AM
  3. Zogundar's Avatar
    The nearest equivalent setting is Network Mode and it's set to "LTE/WCDMA/GSM (auto connect)." It doesn't have an LTE only mode.
    03-06-2018 03:03 AM
  4. B. Diddy's Avatar
    What is your VoLTE option set to? Try toggling that either on or off, depending on what it's set for now: https://support.t-mobile.com/docs/DOC-22754
    03-06-2018 03:42 AM
  5. Zogundar's Avatar
    Already tried that (It was on, I turned it off, no effect.)

    However what I had not tried was turning it off with mobile data left on. If I do that I can't make calls. Both VoLTE and mobile data have to be on, apparently.
    03-06-2018 04:44 PM
  6. B. Diddy's Avatar
    It almost sounds like the phone is unable to connect to the 2G network. But unlike AT&T, T-Mobile's 2G network is still active (although I've read that they want to shut it down as well, some time in 2019). Does the phone's cell signal indicator always show 4G, or does it ever drop down to 2G/3G? In that Network Mode menu, can you choose 2G/3G only, and see if it can connect to the network at all?
    03-07-2018 02:54 AM
  7. Zogundar's Avatar
    If I select WCDMA only or WCDMA/GSM(auto) it says not registered on network when making a call. If I try to search for networks and then pick T-Mobile or Search Automatically it gets stuck.

    Perhaps I should also mention that I had a signal booster installed a while back due to shoddy indoor reception. I've always had mediocre 2G/3G reception indoors but at some point it became markedly worse worse to the point where cell phones were becoming unusable. Installing the signal booster worked like a charm (Until this problem started.)
    03-07-2018 10:41 PM
  8. B. Diddy's Avatar
    Can you confirm that the phone was originally from T-Mobile? You mentioned in your OP that it's a "T-Mobile phone," so I assumed it was originally sold by them -- but I was thinking that maybe you only mean that you're using it on T-Mobile. Was it from a different carrier to begin with, like AT&T?

    Which APN is it using? https://www.androidcentral.com/what-...do-i-change-it
    03-08-2018 10:48 AM
  9. Zogundar's Avatar
    T-Mobile phone: model SM-N900T.

    Standard APN for T-Mobile: fast.t-mobile.com (I've also double checked the settings recently to make sure they match with what it's supposed to be.)
    03-09-2018 04:30 AM
  10. B. Diddy's Avatar
    Have you considered asking T-Mobile for a replacement SIM?
    03-10-2018 12:59 AM
  11. Zogundar's Avatar
    Just now I tried putting the SIM card in a different phone, and I was able to make calls with data (And just in case, Wi-Fi) turned off. So I'm guessing replacing the SIM wouldn't help.
    03-15-2018 05:28 PM
  12. B. Diddy's Avatar
    If you want to take it this far, you could try reinstalling the firmware, in case something got corrupted. You can use Kies (http://forums.androidcentral.com/amb...sung-kies.html) or Odin (http://forums.androidcentral.com/amb...interface.html).
    03-16-2018 01:13 AM
  13. Zogundar's Avatar
    After mulling it over, I've decided against any kind of formatting/reinstall, especially if the problem could be something like a bad antenna that wouldn't be fixed by that (Is there a way to repair/replace those?)

    Probably will end up living with it until I can get a new phone, otherwise.
    03-21-2018 04:57 PM

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