I would like to stop my instances in order to avoid unexpected chages

Today I receive a message telling I would be charged by my aws account. I think it is because ended the free trial time. I would like to deactive all instances and resources in order to avoid unexpected charges. I found in billes it Elastic Compute Cloud USD 1.01

South America (Sao Paulo) USD 1.01

EBS USD 1.01 $0.19 per GB-month of General Purpose SSD (gp2) provisioned storage - South America (Sao Paulo) 5.322 GB-Mo

I entered here https://sa-east-1.console.aws.amazon.com/ec2/home?region=sa-east-1#Instances: and tried to delete the intance of EC2 that I think is the problem. But I couldn't so I don't know if it is active or not.

Also following this page: https://repost.aws/knowledge-center/check-for-active-resources I entered here: https://us-west-2.console.aws.amazon.com/resource-groups/tag-editor/find-resources?region=us-west-2#query=regions:!%28%27AWS::AllSupported%27%29,resourceTypes:!%28%27AWS::AllSupported%27%29,tagFilters:!%28%29,type:TAG_EDITOR_1_0

In the Tag Editor appears a lot of resources: I tried to delete them but it refuse and says it is not possible to delete

This DHCP option set is in use and cannot be deleted. You can't delete a DHCP option set that is associated with a VPC. Associate a different DHCP option set with your VPCs.

Please help. thougth to delete my account but I can not reactivate it in the future. I wait for your help. Thanks in advance.