Display a toast whenever selection on radio button changes

Ionic Framework
1

Below radio group i’m using to display a toast on selection of radio button, but i would like to display toast only once whenever the selection changes, as of now repeated selecting a radio button displays a toast.

below mi .html code

<ion-content class="card-background-page">
    <ion-card style="height: auto">

        <ion-list radio-group [(ngModel)]="Config_URL">

            <div *ngFor="let header_list of headers;let i = index;">

                <ion-list-header style="color:green">{{header_list.header1}}</ion-list-header>
                    <ion-item>

                        <ion-label text-wrap *ngIf="i<headers.length-1"> {{urls[i].url1}}
                            <hr style="color:black">
                            {{urls[i].url2}}
                        </ion-label>
                        
                        <ion-label *ngIf="i==headers.length-1">
                            <ion-item>
                                
                                <ion-label style="color: primary" stacked></ion-label>
                                <ion-input  #input name="BaseUrl" type="url" placeholder="Base url"></ion-input>
                                       
                                <ion-label style="color: primary" stacked></ion-label>
                                <ion-input name="ImageUrl" type="text" placeholder="Image url"></ion-input>

                            </ion-item>
                        </ion-label>
                        <ion-radio value="{{header_list.header1}}" (ionChange)="select(header_list.header1)"></ion-radio>
                    </ion-item>
            </div>
        </ion-list>
      <button ion-button round color="royal" style="display: block; margin-left: auto;margin-right: auto;">Submit</button>

    </ion-card>
</ion-content>

Advance Thanks