Simba Lineker

Okay this is just a general open ended question I have concerning product naming and legalities involved with finding out someone else has the same product under the same name. Events as follows:: Product A is created, named, and released on marketplace and in-world. 24 hours later you are contacted by someone claiming to have the same product, under the same name being released soon. However they have had a group and logo's situated for their product for nearly a year and are demanding you change your own product's name. Now product A is a general product (much like OC Collar's); There are multiple out there, all named differently, and the only difference is the design/texturing. As well as the scripting involved with making it work. As far as the name is concerned, you did a precursory search in marketplace and various other locations; The only thing you found concerning this other persons product; is a group that has been open for quite some time, however seemingly dead; with no notices or even a hint that what they were designing...is still being designed or released. You have also checked with the trademark offices and find that the name itself is not trademarked either. What are the legalities behind all of this? Your product although named after the other persons supposedly...is fully released and getting upgrades and fixes currently. Their product has not been released and for all you know isn't going to be unless you take their word on it. Name is not trademarked from what you can find out, ect.