TypeError: this.insertOne is not a function, mongoose statics

I’m trying to use mongoose statics, so I followed the docs and so far not working as expected. I have tried a lot of ways to export/import the model. Every time I see a different error, once the functions I made weren’t defined on the model and others type error.

this is my model:

const mongoose = require("mongoose");
const Schema = require("../../config/DB").Schema;
const db = require("../../config/DB").db;

//schema
const MessagesSchema = new Schema({
  userID: { type: Number, required: true },
  messageText: { type: String, required: true }
});

MessagesSchema.statics.saveMessage = function(MessageData, cb) {
  this.insertOne(MessageData, (err, result) => {
    if (err) {
      console.log(err);
      cb(err, null);
    } else {
      cb(null, result);
    }
  });
};

MessagesSchema.statics.findMessages = function(userID, cb) {
  this.find({}).toArray((err, result) => {
    if (err) {
      cb(err, null);
    } else {
      cb(null, result);
    }
  });
};

module.exports = mongoose.model("Messages", MessagesSchema);

And this is how I used it in another file:

const MessagesModel = require("../../api/models/messages");
      MessagesModel.saveMessage(
        { userID: message.sender.id, messageText: message.text },
        (err, result) => {
          if (err) {
            console.log(err);
          } else {
            console.log(`result object length = ${Object.keys(result).length}`);
          }
        }
      );

problem solved using create instead of insertOne, since the model doesn’t have it.