Generally speaking, true-hearted Christians refrain from bearing the sword, including instructing others to bear the sword on our behalf. We might feel it proper to notify the magistrate if we see the weak and the vulnerable being hurt, so I might notify the police (or the bank) that an elderly neighbour is being taken advantage of in a financial scam. We would even notify the magistrate if, for example, a miscreant were hurting our children, or even ourselves, as that is the magistrate's domain.
However, we would avoid asking the magistrate to bear the sword strictly on our behalf for our own gain. So we would not go sue at law to compel payment from someone we believe owes us something. It is, of course, perfectly acceptable to request that they settle the account.
It seems that sometimes, a plain Anabaptist hires an attorney who then drafts a demand letter.
I am wondering if this is something we should be doing. It is a bit of an "empty threat" - we aren't going to actually sue, but sending a letter from an attorney gives a certain colour of law to it.