How to call API in ionic using post request and by passing 4 parameters?

I am learning to call API in ionic 3 for Sending registration purpose. and I don’t know the proper way to call it.

I have tried to call it but it did not success!

register.ts

if(this.registerData.billing.phone.length!=10)
                {
                    let alert = this.alert.create({
                    title: 'Mobile Number Required!',
                    subTitle: 'Please enter your 10 digit mobile number ',
                    buttons: ['OK']
                });
                    alert.present();
                }
             else
                {

            var val = Math.floor(1000 + Math.random() * 9000);
            console.log(val); 


        let headers = new Headers();
            headers.append("Content-Type", "application/json");
            let options = new RequestOptions({ headers: headers });

            let postParams = {
              request_code: 'send_sms',
              email: this.registerData.email,
              mobileno: this.registerData.billing.phone,
              otppin: val
            };

    this.http.post('myapiurl',  JSON.stringify(postParams),options)

        .subscribe((response: any) => {

             console.log(postParams);
             console.log(response);
         if (response.response_code == "STATUSOK") {
           console.log(response);

                     this.nav.setRoot(OtpcheckPage);

                         } else {

                            let alert = this.alert.create({
                                title: 'Error',
                                subTitle: response.msg,
                                buttons: ['OK']
                                });
                                alert.present();

                        }
                            }, (err) => {
                            let alert = this.alert.create({
                            title: 'Registration failed',
                            subTitle: 'Please check your credentials',
                            buttons: ['OK']
                                    });
                             alert.present();
                            });

                            }

                        }

             }
                }

register.html

 <ion-item>
      <ion-label floating>{{"Email" | translate}}
      </ion-label>
      <ion-input type="email" [(ngModel)]="registerData.email" name="Email">
      </ion-input>
    </ion-item>

    <ion-item>
      <ion-label floating>{{"Phone" | translate}}
      </ion-label>
      <ion-input required type="number" [(ngModel)]="registerData.billing.phone" name="billing_phone">
      </ion-input>
    </ion-item>

My Postman api parameter

request_code: send_sms
email: admkmvkf
mobileno: 9936******
otppin:  1234

My JSON response

{
    "response_code": "STATUS_OK",
    "msg": "SUCCESS"
}

My console giving response of Response

 {_body: “”, status: 200, ok: true, statusText: “OK”, headers: Headers, …}

I want as soon as i click on register button an SMS has been sent to the user mobile number and forward to Otp check page.

Kindly help me to solve this.

Source: AngularJS