Charge generated using RDS, however I was doing a Skill Builder lab

I was doing a lab in AWS Skill Builder on Amazon RDS. In the practical part, I had to create a database, and in the video it was not informed if it would generate costs, so I decided to leave it running. At the end of the month, a high charge was generated, and I used the RDS for studies. I wanted to know if there is a way to solve this without having to pay. I saw that AWS provides study vouchers. How can I get it?