Unlocked Phone only works on Vodafone

[rajs123]

Hello All.

I have a really weird issue with my Samsung Galaxy S8 phone. I am UK based. I used to be on the 3 network and switched recently to GiffGaff due to their very competitive international calling rates. I had no problems on either of these carriers until late last week, when I could not make or receive calls. I was able to send and receive text messages, and use the 4G for internet access.

After trying SIM cards from the different carriers, the only one that works is the one from Vodafone. It seems like the phone suddenly became locked to this carrier.

I was wondering if anyone has come across this before and if so, how did you resolve it? I suspect that my phone is going to stop working soon and I will need to replace it.

Thank you in advance for any assistance that you may provide.

 

[Hadron]

You say "the only one that works is from Vodafone", but you also say that you could send/receive messages and use wireless data. So this isn't like your phone has become locked to Vodafone, because if that were the case you'd not be able to do anything using a non-Voda SIM, you'd just get a message telling you that your SIM was invalid or asking you to enter an unlock code.

So whatever the problem is, it's not that.

So which carriers did you test with, and did you get the same results from each (apart from Voda)? The reason I asks is that if for example you were unable to make calls, but were able to use data, with SIMs from 3, EE and O2 that would be odd, because those are completely separate networks. If however you were in that same position with O2, GiffGaff and Tesco Mobile it would suggest a network-specific problem, because all 3 of those use the same network. So we need more information to know what we are dealing with here.

As for voice not working but 4G data doing so, do you have VoLTE (voice over LTE) enabled? It wasn't commonplace when the s8 was released, so may not be on by default, but it might explain how you could have 4G data working but not voice: without VoLTE the phone has to fall back to 3G or 2G to make a voice call, so if those were not available you could have the symptoms you describe. Maybe worth checking and turning VoLTE on if it isn't already.

For information, EE and Vodafone are both supposed to be winding down their 3G networks this year, and 3 will have turned their 3G off by the end of 2024. So if any problems are due to a loss of 3G coverage it might be due to that rather than some local transmitter outage, in which case it will not be temporary and will probably cover a wider area than just a single transmitter. Curiously the only ones who haven't announced anything about their switch-off schedule are O2, who as noted are the network that GiffGaff use. Whether that means that it's not starting soon, or just that they've not made any announcement, I cannot say.

Nobody has said that they are winding down 2G in the next few years, and lack of voice support would also require lack of 2G coverage, so that is one point against this theory. And it could be something else, but anything else requires a fault in your phone which is somehow not present when using Vodafone or faults in multiple SIMs or multiple networks (unless those SIMs are all using the same network), which is why VoLTE and 2G/3G coverages are the first things I'd check.

 

[rajs123]

Thank you for your detailed response Hadron. I did try a SIM from O2, and has the same problem. I also tried a SIM from Lebara, which uses the EE network, but their SIM could not even register on the network.

All the phone repair shops that I visited were completely baffled by this problem. The fact that my GiffGaff SIM worked in another phone leads me to believe that my S8 is slowly "dying". I went ahead and purchased a Pixel 6a, primarily because it had good reviews and I wanted a small screen size.