Anonymous Phone Calls

Well, while I was travelling by train this evening, I called the information-hotline of t-mobile one of europes biggest phone-companies, in order to ask for a number. As I`ve told the young lady the name of the company, our train went into a tunnel, and the connection broke – but guess what: some seconds later I got the requestet number via sms. But how did they do that? I certainly have supressed my number – nobody should be able to identify it. Is there a system, which is able to make the number clear? Strange happening…