Hey, I'm hoping someone can clear this up for me.

Short version:
I think that companies or people with 0800 phone numbers (and maybe other 08 numbers) can get a caller's phone number, even if the caller tries to withhold their number. Right, wrong, or it's complicated?

Long rambling version:
I got this idea from somewhere - I think it was from sales info for an 0800 service - but I dunno if I just got the wrong end of the stick or misinterpreted what I read. I now cannot find the same info, but I have been told that I am wrong about 08xx number callees getting a caller's CLI even if the caller precedes the 08xx number with 141 (on a BT land line). I have tested it once though, and an 0800 number callee did know my number after I had withheld it.

Maybe where I saw this info were also offering a further service to pass on the CLI (telcos get the CLI no matter what), but to be honest, businesses with 0800 numbers for the sale's lines would probably love to be able to get caller's numbers who just make an enquiry but don't tell the company any personal details. The business can track callers/customers, or they can call back and try for a sale (even though this is against OFCOM's rules or the DPA. I worked for a few weeks at a mail order company where the boss was very insistent that all caller's numbers were noted down, and they were used for later spamming).

I seem to remember that the justification for 0800 number operators getting the CLI no matter what was that as the 0800 number operator is footing the bill they deserve access to the data, like a normal phone line customer deserves the choice of an itemised bill.

I tested this 0800 callees getting withheld CLIs though. I rang my mobile from my BT land line preceding the number with 141, and it said "withheld", as expected. I then called the Job Centre on 0800 055 6688, preceded with 141. When the guy at the JC wanted my contact number, I said it was the number I was calling from. He had the number right there, so it can't have been withheld as I expected. The Job Centre aren't an emergency service. They aren't a telecoms provider. WTF?

If the JC can do this, who else can? And does it apply to other 08xx numbers, like 0845 or 0871?

Ultimately I am trying to determine how accurate the lines like "Anyone with further information is asked to call .... Crimestoppers anonymously on 0800 555111" that gets slapped on the end of many tin-pot local-rag news articles. I want to know if anonymous means anonymous.

No, I'm not looking to be a grass. I want to know if I am being lied to. I think I am, as my experience tells me that calling an 0800 number is not anonymous, even if you want it to be.

Cheers

(Just to add some value to this post, my technique for avoiding 0870 etc. numbers is to call numbers next to a company's published fax number. Companies frequently have 08xx for sales, support, etc., but often the fax number a geographical number. As companies routinely have numbers in blocks, calling numbers around the fax number will often be a direct dial number to someone's desk extension. Just get whoever answers to put you through to the right department! This trick is probably widely known around these forums, but you never know ;) ).

This is the brief version. If necessary I can look up the detailed references.

There is a difference between the full CLI and "location data", i.e. enough of your number to place you geographically, in simple terms, your local telephone exchange.

Location data is available to those you call if it helps them direct you to the appropriate local service centre. It can also be used to show that you are not calling an "international calls only" number from the UK. Obviously it is not that precise and can be misleading, or totally absent in the case of Skype for example. Those who use it have to be aware of this and have a fall back.

Perhaps the best known example is 0845 4647, which is used by both NHS Direct and NHS Direct Wales - two separate services.

There is something similar available for mobile calls, where the cell from which you are calling can be identified. This is proudly used by one of the motoring breakdown companies to locate an ex-footballer and actor as I recall.

The full CLI is subject to statutory privacy protection. The relevant legisation draws a very strong line between that and the location information, for obvious reasons. That line may have been missing from your understanding of the situation.

There is, of course, absolutely nothing to stop you using a dial-through service such as 020 0222 0900 to ensure that there is no possibility of your number seeping through ..  Of course, you'll then be paying for a geographic call to London, but that's cheap enough, or possibly free depending on your calls package.  This is usually what we suggest for callers from Mobiles to avoid the extortionate charged made to 080* numbers, but I can see it working for your case too.

(Disclaimer: I've not tried it, and perhaps you should before you rely on it, but I don't see how they could justify both obtaining an incoming withheld CLI, and then presenting that on the outgoing call - there are regulations that would prohibit both those actions.)

Further to my previous posting - this has got nothing to do with 0800 or any other special number that you may be calling.

Location data is available and full CLI protected whatever number you call.

The only way that this could be broken is by a crooked telco.

Make up your own mind about whether you trust dial through providers more than the end telco.

This topic has been discussed previously here.