Dear sir, as per your querrry, i would like to inform you that, since you are not the registered trade mark of your company's name, you have to show sufficient proofs before the court of law inorder to substantiate your case i..e you have to establish that, you are using such name from the last 20 years by showing some invoices, bills, business on such name. First you check yourself with the availability of these things with you. If you confirm that, you are in use of such mark from the past several years then you can give a legal notice to the infringed person stating that, you are using so and so mark from so and so years and people have recommonded your mark in the market and you have a good business only becoz of such distinct name in the market. You may ask him to not to use the mark from now onwards and also to demand him to pay compensaion for the loss or damaged caused to you by using your name. If at all that person has stopped using such name, then its ok. But, mostly that person will not stop there itself and tries to approach court of law before you approach there. So i suggest you to follow some of below guidelines;
1. You first make an applilcation before the Trade Mark registry for registration of your trade mark name.
2. You also file a Caveat before the concerned court so as to stop the other party to approach the court of law before you approach.
3. Through legal notice you give 15 days time to stop using the trade mark, and immediately after that, you file a civil suit before the concerned court.
It is always better to approach a competant Advocate for taking necessary action.