I would send them a letter documenting your services, when you invoiced them (and a copy of the invoice), when you attempted to contact them, and then end the letter with a clear threat to use legal action if they do not pay within a certain period of time - give them 10 days and send your letter by certified mail with return receipt. You could take this to small claims court and probably win even if your contract was verbal. You can ask for a judgement in the amount of your invoice, interest, and court filings costs (anywhere from $25-100). Usually a letter from you and then a summons notice from the court quickly gets people who are "reasonable" to pay, since a judgement against them can haunt them for years and most sane people will not risk it for a mere few hundred dollars. However, you never know.
Hell, I would take them to court just so you can learn how the process of suing someone works and how to prepare for the case. You never know when it might come in handy in the future. In my business, we routinely sue companies and people who do not pay up, and we have won judgements even when the order was called in over the phone and we have no records of that conversation other than the invoice and shipping documents we can provide to the court. Usually the court looks upon the actions of the debtors, in that, if you invoiced them and contacted them repeatedly and they did not contact you, the court will sometimes look at their actions as being stalling in nature and may rule in your favor. I still say that since the amount is $400 and it is obviously important to you, do this as a learning experience when you need to go after real deadbeats in the future.
Once you get judgement against them, then getting them to pay might still be difficult. You can usually have the local sheriff take action against them. If you know where they live and what property they posess (cars, trucks, etc.) you can have the sheriff seize those to pay off your debts. I've had some of my deadbeat customer's trucks and cars booted by getting their make/model/license plate/VIN to the local sheriff and have them execute on that. Having a car or truck they use everyday booted up quickly gets their attention.
There are so many options, and it just best to call the Clerk of Court at your local Magistrates or Small Claims Court in your local county or jurisdiction and ask about the procedure.
It is surprisingly effective and judges tend to favor honest business people with good records.
Hope this helps and go get them.
Next time, remember to get a signed contract clearly documenting your agreed intentions, payment schedule, and have a clause about what collection method(s) you will use and how those costs will also be borne by them.
Pradeep
See here:
1. http://www.gov.ns.ca/just/selfrep.htm![]()
2. http://www.courts.ns.ca/smallclaims/cl_info.htm![]()
3. http://www.courts.ns.ca …small_claims_brochure.pdf![]()
It seems that Small Claims Court fees in Nova Scotia are $80 CAD. If you are serious about doing business and running a business, I'd consider that an investment of your time and money to learn how to sue someone properly and efficiently. 


