You should be able to determine if a law office contacted you, because this sounds more like a collection firm.
Collections firms that threaten criminal prosecution, likely violate the fair debt collection laws.
You should keep a record of contacts and what is said, as you have started.
You should be able to verify who you are speaking to, they can send you a letter, for example.
There are other ways to get in trouble, such as, did you give any post dated checks, provide false statements, take out the loan not intending to repay it?
You would benefit from contacting a debt defense attorney, and also, by making no more pay day loans.
General legal advice is offered for educational purposes only. A consultation with a qualified attorney is required to determine specific legal advice as to your situation and applicable law. We are a debt relief agency and we help people file for relief under the bankruptcy laws.
The one who called you likely violated federal and state laws.
What you should do, should they call you again, is to tell them not to call you again.
What you should also do is report the caller to the Attorney General at www.atg.wa.gov .
The AG is not going to be your attorney. However, the AG can and does sue companies that violate WA laws. The AG usually acts when there are enough persons complaint about a company.