I just read an article about someone who sued a company with help of a lawyer from Lemberg Law because of this robocall problem. (nystateofpolitics.com)
If a violator ignores your letter, you should write a cease - and - desist order with the help of a lawyer native to the perpetrator's country. (inc.com)
With the help of his lawyer, the accused had two strategies: abonos (finding favourable witnesses) or tachas (demonstrating that the denouncers were prejudiced). (faith.org.uk)