Call number after alert doesn't work

I create a very simple code for call a number after confirm on an alert popup.

After confirm the call doesn’t start

This is my code for .html

<ion-item *ngFor="let item of emergencylist" (click)="emergencyCall(item)">
  <ion-row class="center">
    <ion-col width-80>
      <img src="assets/img/buttons/{{item.id}}.png">
    </ion-col>
    <ion-col width-20 class="icon-call">
      <ion-icon name="call"></ion-icon>
    </ion-col>
  </ion-row>
  <ion-row>
    <ion-col>
      <p>{{item.desc}}</p>
    </ion-col>
  </ion-row>
</ion-item>

This is code for .ts

 this.emergencylist = [
      { 'id': 'police', 'name': 'Police', 'number': '+39112', 'desc': 'National helpline for all emergencies, to report robbaries, thefts or assaults, accidents ecc.' },
      { 'id': 'carabinieri', 'name': 'Carabinieri', 'number': '+39113', 'desc': 'Dial this number to access Carabinieri police headquarters. Foreign language response service available' },
      { 'id': 'firebridage', 'name': 'Fire Bridage', 'number': '+39115', 'desc': 'In the event of fire, smoke or gas leaks, you can make a direct call to this number' },
      { 'id': 'healthcare', 'name': 'Healthcare', 'number': '+39118', 'desc': 'Healthcare / Ambulance network for transport to the closest hospital or health facility' },
      { 'id': 'roadassistance', 'name': 'Road Assistance', 'number': '+39803116', 'desc': 'Number to dial for roadside assistance, if your engine breaks down or in the event of another problem with your car' },
      { 'id': 'forestrycorps', 'name': 'Forestry Corps', 'number': '+391515', 'desc': 'Environmental emergencies, especially forest fires' },
      { 'id': 'coastguard', 'name': 'Coast Guard', 'number': '+391530', 'desc': 'Helpline for emergency situations in Italian waters' }
    ]

emergencyCall(item) {
console.log(item.number);
let alert = this.alertCtrl.create({
  title: 'Are you sure?',
  message: 'Do you want to call the ' + item.name + ': ' + item.number,
  buttons: [
    {
      text: 'Cancel',
      role: 'cancel',
      handler: () => {
      }
    },
    {
      text: 'Call',
      handler: () => {
        console.log(item.number);
        let browser = new InAppBrowser('tel://' + item.number, "_blank", "EnableViewPortScale=yes");
        browser.show();
      }
    }
  ]
});

alert.present();
  }

Why are you not using the Native Plugin call number?