I&#x27;m not sure whether it&#x27;s the reason T-Mobile is asking for it, but a number of countries have added identification requirements for mobile-phone services, due to pressure from law-enforcement agencies, who don&#x27;t like the possibility that people can buy anonymous &quot;burner&quot; phones &amp; SIMs. In Denmark nowadays nobody will sell you a SIM without tying it to a national ID number. Bank accounts have similar requirements, to combat money laundering and tax avoidance.