Hi & if this has already been answered, or does not work for you - please forgive. I also do mention a carrier name because I'm personally using it.
Here is my resolution (short version) followed by all the frustration & steps to get there. (just in case you are really, desperately bored & want to read !! LOL)
My guess is: it is possible a device/phone purchased from the specific cellular reseller, might have some either software or hardware added to it - to enhance or track it on that network, (my computer guy tells me they don't do that anymore)
But that an absolutely perfect device, brand new, unlocked & purchased directly from the manufacturer, when using a third party cell service reseller, may not not have that provider software or programing on it to maintain some connections & it doesn't automatically handshake with the re-seller's network when the signal is dropped.
2023 & 2024 - full two years, I had identical problem with my factory unlocked Note 20 when I changed carriers to use a third party reseller ( cable company) to save $.
My cable company offered significantly discounted service (which they purchase from T-Mobile) I bought an inexpensive Samsung A53 or something from them to test. The service was absolutely exceptional!!! and the price was even better. I also saved $15 on my cable TV/Internet.
So I kept the little A53 and moved my fairly new totally unlocked dearly loved Note 20 - to the cable company which re-sells T-Mobile. I constantly lost connection when traveling - the signal would get weak & when it did the circle slash for no service it would NOT reconnect without a reboot or turn on airplane mode and then back off to restore connection. But, that inexpensive Samsung A53 from the carrier, regained service instantly , so I knew the third party carrier had great service, and moved my primary phone number too the third party carrier
Service would frequently disappear & I would get the circle & slash indicating no service - and my factory unlocked Note 20 phone WOULD NOT regain service even when the service was EXCELLENT without rebooting or, turning on & off airplane mode
So, after months of every technical assistance from the carrier, all the way to Samsung tech support, (wiped & redid the phone, etc), and trying every trick on these forums, I purchased the new S24 Ultra also directly from Samsung & unlocked. It STILL Had the same problem. I was absolutely devastated & had spent money I didn't have trying to fix this.
I fought for two years with this and finally noticed my local cable company cellular service reseller, was no longer discounting my cable bill by $15 .
So, with no benefit any longer, and I moved one phone directly to T-Mobile & I have NEVER EVER lost service again except in a total complete dead spot for all carriers. I even have much better service with the extra 5g UC they have that was not included with the cable company reseller. I don't have any clue why a reseller of one of the big three cellular companies is not able to keep a brand new flagship, top of the line unlocked phones on their service, when a cheap A43 or something that they sell you works perfectly - But that was my specific problem, and I moved my old Note 20 over also and it works absolutely perfectly now directly on TMobile. (My area is rural but has good Tmobile. I'm told by folks who understand that the band width they use is slower but it travels further. ) I now only lose signal when there IS no signal, and both the Note 20 & S24 Ultra seamlessly move right back into service when service is available. Hope this helps - Kathy
