Unless you had an employment contract or union agreement, you were an "at will" worker. This means that your company could have changed the terms and conditions of your employment (including your pay rate) at most any time/for any reason, even if you had a mutually agreed upon wage. That having been said, this is true as long as your pay decrease was not applied retroactively. In other words, it could not have been applied for work that you already performed. Accordingly, if you were paid less without notice of the reduction, you can file a wage claim with your state's department of labor.