reactive form pre populate

import { Injectable } from '@angular/core';
          import { Observable } from 'rxjs/Observable';
          import 'rxjs/add/observable/of';
          export interface ICustomer {
            firstName: string;
            lastName: string;
            mobile: IMobile[];
          }
          export interface IMobile {
            number: string;
          }
          @Injectable()
          export class DataService {
            constructor() {}

            public getCustomer(): Observable {
              return Observable.of(customer);
            }
          }

          const customer: ICustomer[] = [
            {
              firstName: 'John',
              lastName: 'lews',
              mobile: [
                {
                  number: '07948714465'
                },
                {
                  number: '07543754465'
                },
                {
                  number: '07543754465'
                }
              ]
            },
            {
              firstName: 'John',
              lastName: 'lews',
              mobile: [
                {
                  number: '07948714465'
                },
                {
                  number: '07543754465'
                }
              ]
            }
          ];