To protect yourself and any evidence that may be obtained during the phone conversations I would suggest you get a court order allowing you to monitor calls with someone else or at the minimum advising the other party they are being monitored.
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Note this answer does not constitute legal advice, and should not be relied on. Each situation is fact specific and court specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship
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