Cellphone records may be subpoenaed like any other information by filling out a proper subpoena form, notes Washington LawHelp. These forms must be issued to you by the court clerk and signed by the judge or commissioner if you are not a practicing lawyer.
Washington LawHelp gives a fairly detailed process of the exact steps that must be taken to get a proper subpoena filed. Once you fill out the subpoena, contact the company that operates the cellphone records in question. The IACP Center for Social Media website has a broad listing of different contacts for both phone and online communications, and others may be found through a direct search of the carrier's website. The subpoena must then be served to the company through its legal channels.