Stop RDS db.r6g.2xlarge charges after changing to Serverless V2

Hi, I am new to AWS. I set up an AWS Aurora database and my initial instance class was Memory optimized classes (includes r classes) - db.r6g.2xlarge. After three days, I realized my usage was too low and the instance class was too expensive. I, therefore, decided to change to Serverless V2 but my bill is still adding db.r6g.2xlarge charges. How can I stop these charges from accruing?

Kindly assist.