Couple of general tips
Don’t approach your boss’ lawyer to try and get a feel for their position. They won’t give you anything and you may inadvertently say something that could affect your position.
If you can get some decent free advice (particularly from a specialist in this field) then recommend that you do, but speaking purely anecdotally, in my experience general purpose legal aid lawyer are pretty hopeless (there are I’m sure huge exceptions to this general rule, but anyway). Appreciate that this may be completely different in Norway though.
When corresponding with their lawyer, try to look as organised as possible. You want to give the impression that you are going to be a something of a chore to deal with (but without being belligerent or rude) so that the advice s/he gives to your boss is that it will probably cost more to deal with you or contest it than it would just to give you your money. I can see that you have saved information that may be useful for your case. I would refer to this and let them have examples if they ask for it. DO NOT give them everything though – confirm that you still have more if they need to see it. If they want you to set out your position, do so systematically and if there’s parts of your employment contract that are woolly or unclear point this out to them also.
The above said it will depend upon the person you are dealing with is an in house company lawyer or someone in private practice the company has employed. If it is the latter, this strategy will work much better than the if it is the former (you’ll be able to tell which it is from the correspondence you receive from them).
Try to avoid phone calls and correspond by email only. It’s easier to give the impression that you are super organised in writing than over the phone when it more easy to get flustered. If they ask for a phone call, unless you feel super comfortable, make an excuse and confirm to them that you would prefer to correspond by email. (This will also be more expensive for them).
Try to be cordial and pleasant if you can. If this lawyer regularly deals with employment dispute, s/he is probably used to getting screamed at. If you are pleasant to deal with and have an arguable case, they are more likely to advise your boss to give you what you want (particularly if it’s not a huge sum of money). If you give them a hard time, they’ll just pull the shutters down and make life as difficult as possible for you.
Are there confidentiality clauses in your employment contract? Bit of a nuclear option, but if they are really digging their heels in you can always threaten to go to the press / social media and say what a dreadful employer they are (taking advantage of seasonal temp staff etc.). If there is a relevant authority in Norway you can complain to, it would be worth looking into so you can threaten this as well.
I know it’s not directly relevant, but the Temporary Agency Work Directive 2008/104/EC is an EU Directive that guarantees temporary staff equal pay and conditions with employees in the same business who do the same work. I know Norway is not an EU Member State and has a complex relationship with EU law provisions, but this might be worth throwing at them too if there is a part of Norwegian law that is comparable. I’m not an employment lawyer though which is why it would be good to get some specific advice if possible. Good luck with it.
