I worked for vos plce and joined the union. im sure i was slandered out of?

out of my job by the son of the owner of vos plumbing. He plays cards with one of the owners of the new company i went to work for in the union . My new boss at harvey and price told me the son of the owner of the last co, i worked for at vos plumbing was bad mouthing me at their social gathering . I ended up losing my job over it. Vos plumbing used unlicensed plumbers the whole time i worked for them some of witch lied about my work and me in general I compained to the building codes department but they dont seem to care why do i have to go through a 5 year state program only to get treated like this is this slander should i get a lawyer ? I so upset over this i find it hard to work this only the tip of the ice burg many other similar things happened in my apprentiship- im to upset just thinking about it to even go back and correct the selling what should i do ?