Persistent "Emergency Calls Only" fault across three SIMs, two phones, two networks — genuinely stumped
The problem: whenever I add a second SIM to my phone, my ID Mobile SIM stops working almost entirely — voice, text and data all drop out, most of the time.
Background
I had a Samsung Galaxy S21 Ultra with an ID Mobile SIM, working perfectly. I added a second SIM (Vodafone, I believe) and the ID Mobile SIM lost connectivity immediately. A reboot didn't help. Even after removing the Vodafone SIM again, my ID Mobile connection showed "Emergency Calls Only" — no voice, text, or data — the vast majority of the time.
First fix (sort of)
Several trips to Currys and multiple SIM swaps later, one sharp-eyed staff member got it working again — but even they couldn't tell me what had actually fixed it.
It happened again, 18 months later
I used the phone's normal dual-SIM function again, and straight back to "Emergency Calls Only." To be precise about "most of the time": on home WiFi, calls and texts worked fine. Off WiFi, nothing. I tried toggling airplane mode repeatedly and would occasionally get a signal, but it vanished the moment I moved to a different cell tower — and this wasn't tied to specific locations I regularly visit. I travel a lot, and there was no pattern to where it worked and where it didn't.
Second fix attempt — no luck
Three different Currys branches, several "experts," multiple new SIM cards — nobody could reproduce whatever fix worked the first time. Eventually I gave up and PAC'd my number to SMARTY (still on the Three network).
SMARTY was no better
The exact same "Emergency Calls Only" issue returned off WiFi — and this time without a second SIM anywhere near the phone. I asked an AI assistant, which suggested a "bad network provisioning" issue. I raised a support ticket, then escalated to a formal complaint, but SMARTY couldn't find any fault with my "provision" and tried to pin it on the handset. So I bought a brand new Samsung Galaxy S23 Ultra, put the SMARTY SIM in — just the one SIM, nothing dual about it — and… still "Emergency Calls Only."
Back to ID Mobile — same result
Now fairly convinced this is a network issue rather than a phone issue, I PAC'd my number back to ID Mobile. And yes — "Emergency Calls Only" is back, most of the time.
Where I've landed
Three different SIMs, two different phones, two providers that both run on Three's network, and the same fault every time it followed my number. At this point I'm starting to wonder if the issue actually lives with my specific phone number's record somewhere in Three's core network, rather than any SIM or handset — but I have no way to prove that myself.
What I'm asking:
Has anyone seen this before, or does anyone know how to get it properly investigated at a network level rather than just being handed another SIM card? I'm 29 years into this phone number and reluctant to give it up, but I'm running out of ideas. Genuinely grateful for any pointers.
