When we try to share a file through Teams and the same name already exists and we would like a copy to be sent, the expected behavior is auto create the file to available name in the same folder. However it seems Teams tries to blindly increase the name by a number without checking the existence of such a file.
Since the community has not yet responded to your post, you might want to contact Microsoft Support directly or open a case at answers.microsoft.com, where there are support agents available to help with further troubleshooting with you until your issue is resolved.
Since the community has not yet responded to your post, you might want to seek assistance with other resources that are staffed by authorized Microsoft agents:
Ask your IT manager to open a support case or call Microsoft using the support line you were given. Other options for business subscription admins are listed here: