It ahs always been well known that giving Sirius something he has ever seen before is dangerous, especially when that something requires electricity. His mother learned this when he was at a tender age when she was destroying the neighbor's (a muggle, for pixie's sake!) things.
"REDUCTO!" she screamed. The telephone smashed the window, a smoldering hole in the centre. Mrs. Black giggled evilly. She loved this. "Sirius," she said, picking up her baby. "See this?" she gave him the cell phone that had been lying on the table. He snatched it immediately from her manicured hand and proceeded to inspect it carefully. Finally, he pressed the same button three times and was delighted with the little beeping noise that thus emitted.
And then the phone spoke. "Where are you? Who are you? What happened?" Sirius laughed. Mrs. Black cackled and kicked over the coffee machine. The message playback began.
"You have reached Ted Wickenham, flat fourty-three…" Sirius threw the phone across the room to see if it had any effect. It didn't.
Mrs. Black tired of destruction after another two minutes (she had already been there twenty minutes, after all) so, at precisely two thirty-four P.M, Greenwich Mean Time, Mrs. Arglethiel Black and Sirius Black left the house of Ted Wickenham, flat fourty-three.
At precisely two fourty, a police car went speeding toward flat fourty three.
You see, the key that Sirius had pressed repeatedly, as luck would have it, was nine.