Dynamic checkboxes in angular2 forms

I have an array of services with following structure: - addonOptions[] - hasAddons - serviceId addonOptions[] has objects with following structure - serviceId - addonName - addonId - isChecked

I loop through services and generate dynamic check boxes where serviceId's match. Now I want to check the checkboxes by default in case isChecked is true. But following is not working.

<ng-container *ngFor="let service of serviceOptions; let i = index">
    <label *ngIf="service.hasAddons"><b>AddOns</b></label>
    <p *ngFor="let addon of service.addonOptions" >
        <ng-container *ngIf="service.serviceId == addon.serviceId">
            <md-checkbox formControlName="addonName" type="checkbox" [ngModel]="addon.isChecked" [checked]="true" (change)="selectServiceAddon($event.checked,addon)"></md-checkbox>
        </ng-container>
    </p>
</ng-container>