Call() is not working on iOS 11+

call() is working on Android but it is not working on iOS 11+.

call() {
    if(this.phone) {
      this.callNumber.callNumber(this.phone, false)
        .then(() => console.log('Launched dialer!'))
        .catch(() => console.log('Error launching dialer'));
  }
}

i set up same as the other project which is working properly on Android and iOS 11+.
Anyone can help me to solve this problem?
i have no idea which files should i check.

Thanks.