I'm using an HTTP post. Not using a SOAP package, just a standard request library (https://www.npmjs.com/package/request). 
Here's the request code: 
request.post({
 url: `https://www.methodintegration.com/MethodAPI/service.asmx/MethodAPIInsertV2`,
 form: {
 strCompanyAccount: process.env.METHOD_ACCOUNT,
 strLogin: process.env.METHOD_USERNAME,
 strPassword: process.env.METHOD_PASS,
 strSessionID: '',
 strTable: 'Contacts',
 arrInsertFieldsArray: ['FirstName', 'LastName'],
 arrInsertValuesArray: ['TestFirst', 'TestLast']
 },
 headers: {
 'Content-Type': 'application/x-www-form-urlencoded'
 }
 }