The sensitive point here is the content of the changes made by the competitor company. In this context, the first step to be taken is to determine whether the application made by the competitor is within the demands of your application. If your application is prepared by an expert patent attorney, he will keep the demands as wide as possible she can, thus it will lead to the prevention of rival companies from eliminating your application with simple changes. Secondly, the fact that whether the product added in the utility model of the competitor is indeed an invention, in other words, the fact that whether it has a technical advantage over its similar ones should be evaluated in the light of the opinions of an expert attorney. Thus, in the general way of action, in order for a product to have the right of Patent/Utility Model, it must have an invention feature essentially.
As a result of the work done in either way, if you find that the product does not contain an inventive feature and/or breaches your utility model, your next move must be to appeal to the competitor's utility model after it has been declared in the Official Patent Bulletin.
On the other hand, when you have a development, before you apply for a patent/utility model, you should think like, "If I were a competitor company, how would I imitate that?", in the light of that insight, and you should put forward a variety of alternative structures in your mind and inform your patent attorney about this before the application.