Not receiving SMS messages I recently switched phone provider, and since then many of the messages sent to me never show up, as if it was never sent. But the sender shows it as sent (though I think it can't know it's been delivered).

I was with my old provider for ~10 years, I use SMS a lot and never had a problem receiving them before I switched provider. I've had my Samsung S6 for 2-3 years now, running Android 7.0 now.  I use Google's messenger, currently known as Android Messages, up-to-date via Play Store.

The problems seemed to start the moment I switched SIM card. The phone is unlocked, and I am receiving "most(?)" of the messages. It's worth noting that my old provider was "3" and the new one is "Spusu" which uses 3's network. Definitely not related to the sender; this is a problem from any person, any company, any network, even any country. 

Seems it's not related to my current location or current time, nor signal strength. I now carry 3 phones -- my S6 with the new SIM card, a spare phone with the old SIM card, and my work phone. Every hour I send a test SMS from my work phone to both my own phones. The old SIM always receives the message, the new one misses some at random. 

I've spoken to staff with the new provider and they claim that all messages have been delivered to my phone, per their log files.


They claim that the Samsung S6 is known to have this problem - but I never experienced it with my old provider, so I don't believe that.
They told me to clear the cache of my SMS app.  I did, but no change.  I rebooted, no change.  
I received a replacement SIM card from the new provider. No change.
I even went as far as doing a complete factory reset of my S6! I hoped this would either fix the issue or rule out the device. Still didn't help. 
Is the Samsung S6 really known to "throw away" SMS messages?
Can the provider really see that my device received the message?
How can a phone receive ten SMS messages and some would randomly be missing?
How can I further troubleshoot this? How can I fix it?


This is a serious problem because everyone I know uses SMS a lot, and suddenly I can't trust it because who knows when a message will go missing again?

I must have SMS capability back. It's no help suggesting some other app.
I can guarantee that this is not a problem related to your phone. Some 15 years back, I had a network provider that did the same, and ultimately I had to switch over to some other network.

Since the problem started soon after you changed your service provider, you should contact your new service provider. There's nothing wrong can do from our side to help you.