Unless you bought a pixel, graphene’d it and then paid a homeless person to activate a pre-paid data only sim which you would top up with vouchers paid in cash and used a von and international voip service…
A lot of effort though
For me the main use is that I'm on o2 in the UK, but if in some dead spot with no signal I can flip the sim settings and connect via EE or whatever.
Why not just get an EE SIM if that's your main use?
And the easy answer is that T-Mobile, or rather the parent Telekom, is a terrible company best known for right now for getting the government to agree that they can cancel your existing internet contract to make switching easier when they want to catch you as a fiber customer but actually all they’re doing is sending a marketing company around Germany (Raider Marketing) to lie to your grandma to sign contracts for the Telekom or just cancel your existing internet contract because they think with a bit of pressure they can get you to sign up with them.
Alternatively, they are also known for the worst peering on existence because they have the crazy idea that they can charge tenfold what other ISPs take for peering because they are the Telekom…
In summary, the Telekom is such a terrible company that I’d rather not give them any money and if I needed T-Mobile coverage I’d rather get a foreign eSIM and rely on roaming than giving them a single cent.
This is very wrong. In Germany you can go to any shady kiosk in a big city and buy a pre activated SIM card invariably registered to some Arabic or Pakistani name.
You can buy it in cash. Completely untraceable if you take care of CCTV.
They might go an ask Achmed some hard questions later, but he’s long since left the country and never met you anyway.
And this is while you're flagging yourself heavily by (1) using a phone which is easily identified as a burner and (2) using it intermittently which means you're trying not to be tracked.
So you've already substantially identified yourself in any dataset.
One of my hobbies is Recreational Paranoia. I used to have (probably still do in a drawer here somewhere) a 3G WiFi hotspot, with an Arduino and GPS module that powered down the battery within a few km of home (actually, within a few km of a public library that's a few km from home, so plotting all the power up & down locations would centre on the library not my house). I could then leave home with that in my backpack and instead of my phone take a wifi only device - I mostly used an iPod Touch but also sometimes Android tablets. I wouldn't get actual phone calls sir SMS that way, but those are both rare for me, most of my social comms are via Signal which worked just fine.
I figure wifi cellular hotspots are "not easily identified as a burner phone" and that intermittent use of them is the most common case. It would still have been able to be tracked as being a thing that turned on and off in my surrounding suburbs, and I'm sure I slipped up last least a few times and had it with me while I also had my phone with me - but like I said this was for my hobby, not running an international drug cartel or doing journalism critical of Saudi Royal houses...
Roaming works somewhat unintuitively from what you'd expect. You do indeed connect to the local mobile network, but all of your data traffic is tunneled back to your home wireless provider's PoP. I realized this once I checked what websites I was visiting saw as my public IP address, and it was an address from a network in Texas!
So China's Great Firewall can't actually inspect or block your traffic while you're traveling, and using roaming on your home mobile network's SIM. It's all sent over the equivalent of a VPN to your home soil before going out to the public internet. This iswhy latency can be pretty bad while roaming.
I imagine they simply don't allow selling such SIMs in China. It would be extremely easy to track and flag any that were e.g. used for longer than a few weeks.
My impression is that people can get VPN access (and like people working in certain domains will just get VPN access through work) pretty easily in China. Though my deeper impression is most people are just fine.
You're not begging to get onto some chinese social network right?
You are not bypassing any firewall as your traffic is actually happening at home. If you access local sites, traffic is coming from home.
I'm suspecting that that post-4G architecture is just formalization of actual commercial deployment. Latency for roaming data was long inconsistent with the 3G diagrams, and exorbitant roaming fees that would be consistent with the diagrams also started rapidly subsiding from late 3G era.
These allow for self activation, have a lockout of 5 failed attempts or so and can be done via sim card codes (not SMS, but you interact with a program on the simcard and low level carrier services.)
Buying prepaid SIMs from tourists or foreign students returning home is a reasonable easy workaround for that - at least if you're the sort of person who meets and befriends those sort of people.
And anyone leaving would have their immigration status expire and the SIM is turned off then unless you provide some other proof of residence.