I had experience with Bing and Google stopping our brand name usage in competitor's ads, in both cases I used online form to contact Bing and Google ad approval teams. The responses from Bing and Google reps were really fast, it took less than 2 business days.Another solution is to create a special group of keywords and ads that contain your brand name and to bid higher than average on these keywords. So when a person searches for your brand product, the first thing that pops up is your ad. Thus, you can supersede your competitors.Besides, if you have resellers or affiliates, you can set special rules for them and forbid online advertising on brand keywords.