We need to work on MVP and customer validation : how can we make the offering more specific and does this get a positive pickup from potential customers?

When I work with my startup clients, we spend an incredible amount of time just summarizing the problem and how you are solving it. This needs clarity of thought as well as some data to back up user sentiment - "do we really need this?"

Let's talk about prevalence of letter writing in your country and if assisted or outsourced writing helps your consumer solve a problem.

Offer to write a free letter for 10 people who have a large following on social media. (Facebook, Twitter or Instagram). In return, if they like what you do, have them post an image, logo and short summary of what you do. Make it simple for them to help share your story.
The key is getting people who value your service tell your story to their friends.

Is there an existing market for what you are selling or are you trying to create a market? If there is an existing market then you have to further determine your target market within that broad audience and the best channels to reach them. Is your target audience on Facebook? More importantly is this the place they go to seek out the services you offer? Spending money on likes is not a wise investment. Ads can be incredibly effective, if your audience is there, and you need to be willing to test the content and photo to get the right combination for your final ad. Before you spend money, it is important to really know your potential customers. I am not a fan of giving away services for free because you diminish the value to prospective customers. Rather than giving away a free service you could start a blog or develop a writing tip sheet. This demonstrates your knowledge and gives them something for free that can build the relationship for a sale.