Your lawyer will explain to you that what you wanted, and what your license terms actually mean, are two different things. There are noncommercial users who have downloaded your software and are using it under the terms of the MIT license. You already gave them permission. Now, they can give copies to commercial users, who can use it under the terms of the MIT license. Your lawyer will explain this to you.
> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software
You can just change the license, that's what MIT allows for. You are allowed to do whatever you want:
You have to keep the copyright notice and notice of existing permissions, but that is not the same thing as a license. And you are allowed to sublicense into a more restrictive license (such as proprietary/closed source). Just not the other way around, which is what the inclusion of the existing notice helps to enforce.