I integrated your code in IONIC 4 mobile App but get error

[gfavour]

Mr Tolu please assist me. I follow your steps on integrating paystack into ionic app.
But get error..."missing command error"...

I import InAppBrowser
import { InAppBrowser } from '@ionic-native/in-app-browser/ngx';

Then I included the same in app.module.ts provider

See the real code during the ChargeCard:

cardNumber: string='';
expiryMM:any='';
expiryYY:any='';
cvc:any='';

async ChargeCardAndSubmit(form:NgForm){

this.cardNumber = "4084084084084081";
this.expiryMM = 11;
this.expiryYY = 2018;
this.cvc = "408";
	
	const loading = await this.loader.create({spinner: "dots",message: "Processing Charge..."});
    await loading.present();
	
	await this.platform.ready().then(() => {
		if (this.platform.is('cordova')) {
			(<any>window).window.PaystackPlugin.chargeCard(
			  (resp)=>{
				loading.dismiss();
				console.log('charge successful: ', resp.reference);
				//this.api.postOrder(form).subscribe(res => {});
			  },(resp)=>{
				loading.dismiss();
				console.log('charge failed: '+this.cardNumber+", "+this.expiryMM+", "+this.expiryYY+", "+this.cvc+", "+resp);
			  },
			  {
				cardNumber: this.cardNumber, 
				expiryMonth: this.expiryMM, 
				expiryYear: this.expiryYY, 
				cvc: this.cvc,
				email: 'chargeIOS@master.dev',
				amountInKobo: 150000
			});
		}else{
		this.api.ShowNotification("Payment plugins not supported on this device","danger");
		}
	});
}