<mat-form-field class="input-width">
                <mat-select placeholder="Plans" formControlName="plans" (selectionChange)="select(plan)"  required>
                    <mat-option *ngFor="let plan of plans" [value]="plan.name">
                      {{ plan.name }}
                    </mat-option>
                </mat-select>
            </mat-form-field>
            <br/>
            ...
            </form