I booked a flight through Flight network/Google an...

I booked a flight through Flight network/Google and accidentally picked the wrong date. I immediately called to correct my mistake. They told me it was a $50 fee. I asked to speak to a manager and they told me they would call me back within 6-8 hours. I never received a phone call. When I called them back they then said my flight was no longer refundable or changeable.
The representative was also very impolite and combative.