WASHINGTON (Reuters) -The U.S. government is urging senior government officials and politicians to ditch phone calls and text messages following intrusions at major American telecommunications companies blamed on Chinese hackers. In written guidance released on Wednesday, the Cybersecurity and Infrastructure Security Agency said "individuals who are in senior government or senior political positions" should "immediately review and apply" a series of best practices around the use of mobile devices. Corporate offerings which allow end-to-end encryption also include Microsoft's Teams and Zoom Communications' online meetings.