Just because it is in your contract doesn’t make it legal!

Realistically it could be worth checking your local laws regarding it and potentially speaking to a lawyer as some will do a free consult to see if you have a case

More or less yes you did American English correctly. More often I just refer to them as semis without adding the truck part, some also call them tractor trailers. It was clear what you meant though so only need to change it slightly if you are going for full American English