The provided source material contains information about complaint letter templates but does not include any factual data regarding free samples, promotional offers, no-cost product trials, brand freebies, or mail-in sample programmes across categories such as beauty, baby care, pet products, health, food, and household goods. Consequently, it is not possible to write the requested 2000-word article on that specific topic while adhering to the requirement to use only the provided source data for all factual claims.
The source material exclusively discusses the use of complaint letter templates for voicing frustrations with retail stores or service providers. It outlines tips for writing effective complaint letters, such as keeping the communication factual, neutral, and professional, and including specific details like account numbers and purchase dates. It also mentions that sample templates provide a structured format with a clear introduction, detailed description, and requested resolution to facilitate proper resolution. However, this information is entirely unrelated to the subject of free samples or promotional offers.
Therefore, based solely on the provided source material, a comprehensive article about free sample complaint letter templates cannot be produced. The available data is insufficient and off-topic for the requested article subject.