I think you can still get around that with some effort.

In 2010, I purchased a dumb phone/sim card for use on a prepaid plan. At the time it was the only way to get onto a super cheap prepaid plan since they wouldn't sell you a sim/the plan directly. I then put the sim into my own purchased smart phones(multiple nexus devices and a one plus one). For convenience reasons, I refill my account online with a cc but I technically could simply buy the t-mobile refill cards for cash then activate the time on them.

As far as I know, there's nothing stopping me from doing this fresh again with a new prepaid phone and then never associating my real identity in any way.

They don't even need to; your telco can know your home address based on a week's worth of location data, and could likely determine more about you based on where you go to work, shop, etc. Humans are creatures of habit, so it's relatively easy to draw inferences from simple patterns (i.e. if you spend 6-8 hours in the same location every night, that's probably where you live.) All it takes is one time checking your e-mail from an IP address to forever link that IP address to you. Know enough IP addresses someone has connected from and you can come up with a pretty good picture of their friend circle, their movements, how old they probably are, etc.

I work in the telecom industry, and this behavior exists because it's not explicitly illegal. This type of data mining is just scratching the surface of their capability -- turns out that a combination of about 30 seconds worth of data scraped off http traffic (not https, though even https can tell you something) and a location are enough to identify most individuals and link them to a profile in a DMP -- which can tell you all sorts of information like which products you've purchased recently (both online and in brick and mortar stores with a credit card), any relevant demographic information, and even what kind of porn you like.

The real restraint on this has been in the use of this information. Marketers have been remarkably conservative in using this information; likely for fear of scaring off customers with "creepy" data. But rest assured they know more about you than you do yourself.

Thanks; that is valuable information. So my whole plan (in the top-level post at the root of this discussion) is hopeless, at least in terms of having anonymous, untracked phone usage?

> your telco can know your home address based on a week's worth of location data

How accurate is that location data, do you know? Within 10 yards? 100 yards?

I can't remember the limit, but it's a legal one not technological. The military has a legal monopoly on precise GPS.

Similar here. I too have used my CC for refills and may have given my name for caller ID purposes, but I don't think it was mandatory nor do they have my SSN or other hard details on my identity.

AFAIK you shouldn't have to get a throwaway phone either. "SIM Card Kit" or "Bring your own phone/device" may be keywords to research -- you should be able to get a SIM that you can put in any GSM phone, and it will come with instructions about a website to visit, or phone number to call, to activate it. If they insist on names etc and it's prepaid, you could give a fake name since it will have no bearing on your ability to use it, although I'd be worried that it might be illegal for some stupid reason.

Go to a smaller vendor like Cricket, they will still do cash prepaid.