My guess is your config file (~/.oraclebmc/config) has Phoenix set as the region for the CLI to work against. If you want to work against a different region, you will have to update the value in that config file, or provide the value via the command line using the --region parameter. Valid values for region in the config file and for --region are available here under the "name" column. For more info, see https://docs.us-phoenix-1.oraclecloud.com/Content/API/Concepts/sdkconfig.htm
I missed the --region switch, thank you!
I see it now in the "main" help output produced by "bmcs --help", but it might be worthwhile to add a note in the help output of the relevant individual commands (e.g., "bmcs iam availability-domain list").