The juvenile court denied mother’s right to due process when it refused to hear live testimony in connection with her section 388 petition. The petitions showed a clear credibility contest between mother and the paternal grandmother, which the court resolved adversely to mother based on written submissions. The court should have received mother’s oral testimony and permitted her to cross-examine the grandmother and the social worker. Since mother’s 388 petition was erroneously denied, the order granting guardianship and terminating jurisdiction also had to be reversed.