AWS Lambda returning without waiting for promises

I have a function working perfectly well within a node environment. The function uses promises, with S3 calls and a then and catch to call the callback with relevant 200/500 statusCode and a message body in each of them.

Now I am deploying it as a lambda function with a wrapper around it looking like this:

module.exports.getAvailableDates = (event, context, callback) => {
  const lambdaParams = retrieveParametersFromEvent(event);
  console.log(`Got the criteria`);
  module.exports.getFilteredDates(lambdaParams.startDate,
                                 lambdaParams.endDate, callback);
  console.log(`Returning without the internal function results`);
};

The internal function looks like this:

module.exports.function getFilteredDates(startDate, endDate) {
  const dateSet = new Set();
  return new Promise((resolve, reject) => {
    const getAllDates = (isDone) => {
      if (isDone) {
        const Dates = Array.from(dateSet).join();
        resolve(Dates);
        return;
      }
      getTestedDates(startDate, endDate, region, func, memory,
        lastDateKey, dateSet).then(getAllDates).catch((error) => {
          reject(error);
        });
    };
    lastDateKey = '';
    getTestedDates(startDate, endDate, region, func, memory,
      lastDateKey, dateSet).then(getAllDates).catch((error) => {
        reject(error);
      });
  });
}

And the even more internal function looks similar, only it actually queries the S3 database and returns the list of keys from it that match the date criteria.

In the AWS CloudWatch logs I see the two prints and only after them the internal function output. My understanding is that the lambda function is not waiting for the internal function with the promises to actually do its work (including the internal waiting on the promises) and returns with a bad status to me. What can I do?