using a function that calls observable with 3 different observables tied together with switch map. results in error

I have a function that runs when a file is uploaded to a html form.

    let subscription = this.s3service.publicresourceuploadtos3(event)
      .subscribe((req: any)=>{

this function calls a function publicresourceuploadtos3 from a injected service. this function is displayed below:

publicresourceuploadtos3(event): Observable<any>{
    console.log('the service at least ran');

    const mediatobeuploaded =[0];
      switchMap((req : any)=>{
        console.log('did the call to the server');

        const resourceurl = req.uriroot + req.fields.key;

        let fd = new FormData();
        fd.append('acl', req.fields.acl);
        fd.append('key', req.fields.key);
        fd.append('content-type', req.fields['content-type']);
        fd.append('policy', req.fields.policy);
        fd.append('x-amz-algorithm', req.fields['x-amz-algorithm']);
        fd.append('x-amz-credential', req.fields['x-amz-credential']);
        fd.append('x-amz-date', req.fields['x-amz-date']);
        fd.append('x-amz-signature', req.fields['x-amz-signature']);
        fd.append('file', mediatobeuploaded);, fd).pipe(
          switchMap((req2: any)=>{
            const result = {
              resourceurl : resourceurl,
              resourcekey: req.fields.key
            return of(result);




the console log console.log('the service at least ran'); does fire in the console but the server call one: console.log('did the call to the server');
did not.

but this results in an error:

ERROR TypeError: Cannot read property 'subscribe' of undefined
    at ContentcreatorverificationComponent.uploadidnexttofacepicture

Im worried this is a syntax issue, would be helpful if any of you know what happening.

Source: Angular Questions