[swinog] How do website operators get the mobile phone number of visitors?

Hi List

I have read:

https://nakedsecurity.sophos.com/2012/01/25/smartphone-website-telephone-num...

And I have sniffed the traffic between my swisscom mobile Samsung Mobile and my Website, but can't find any of the additional headers disclosing my phone number.

Is there a trick to make a mobile phone disclose it's phone number while connected via the mobile network's operator network?

How can 'website payment' operator like 'obligo' get the phone number associated with a visitor? Obligo states they got the phone number to bill 'from the service operator'.

Would it be possible, that a fraudster injects such headers from a client to make obligo bill the wrong number?

PS: I know obligo's reputation.

Mit freundlichen Grüssen

-Benoît Panizzon-