HELP- Czech Republic Tourist Visa refused

Hi all, I have planned a vacation to Czech Republic, Hungary and Austria this December with my Mom and Dad. Since I’m a student, my Dad is sponsoring me. We have made all reservations, flight tickets and presented all the necessary documents in our application.

We got the following points in the refusal letter: 1. You have not provided proof of sufficient means of subsistence for the duration of the intended stay or for the return to the country of origin or residence. 2. Information submitted regarding the justification for the purpose and conditions of the intended stay was not reliable.

The cover letter that we submitted was not very elaborate. Could this be an issue? Can anyone point out what possible reasons my visa got refused even though I submitted every documents. I have to re apply for the visa, because all my bookings are done and the tickets are non refundable. How can I ensure that it doesn’t get refused again. Any help is appreciated. Thanks.