RNBlobUtil fetch pdf with formData

Question

I'm trying to fetch a pdf from an url but I have to send a formData with the request. I couldn't understand how to achive that. is POST only used for uploading files?

     const req = RNBlobUtil.config({
                fileCache: false,
                path: filePath,
                addAndroidDownloads: {
                    useDownloadManager: false,
                    notification: false,
                    mime: 'application/pdf',
                    path: filePath,
                    title: fileTitle,
                }
            })
            .fetch("POST", url, {
                'Content-Type': 'multipart/formdata'
            }, [{param1: 'value1',param2: 'value2'}]);

where am I doing wrong? I can reach the pdf from same url with axios call it responses. but in RNBlobUtil it results empty invalid pdf.