This is not some thing new,
this company has been sending letters to many business owners to demand payment for subscription of listing their company in their website since 2013.
it has been reported in News Papers, countless business owners had been filing police reports, filing complaints with Case against this company, yet last month, they still sent out letters to many business owners demanding payment. they will impose 8% interest if business owner did not pay up on time.
I also received such letter from this company last month. Upon a simple Google search, found out this is just a scam, some victims did paid up, but most of them quickly found out what is company up to.
they even threaten anyone with lawsuit for calling them as scam.
Here are some webpage to know more about this company
I had follow Grace's advice, filed a Police Report and Ignore the letter.
if you have received such letter, I would advice you read up those links I posted and to do the same.