First of all, you have absolutely no way of knowing that, and secondly, that's not even what he says himself jackass.
He says that he rarely uses a cell phone, except that there are many pictures of him talking on an iPhone, and his many daily Tweets come from an iPhone.
So as usual he is lying.
He regularly talks to his rich friends who have business interests in China, and China is using that fact to manipulate him.
His use of an unsecured cell phone makes Hillary's private server look like Fort Knox.