Ifs tjhis a crimional case or a civil suit?
Are you a defendant or an accused in this case.
According to Section 315 of the Criminal Procedure Code, 1973 (CrPC), an accused can be a competent witness for the defence and like any other witness he is entitled to give evidence on oath in order to disprove the case brought against him by the prosecution.
You can file a petition under section under section 315 cr.p.c. to permit you to mark certain documents to support your case.
During cross examination you can ask the witness about this incident of troubling your over phone and get the documents marked through the witness, if the witness denies the knowledge then you can file a separate petition to depose your evidence.
You can produce the device and can request the court to return it after the disposal of the case.