Each time you agree on a term or condition with a supplier, document this back to them in an email.
For example if a rep says if you take a spinner of product from them they will make sure no one else nearby stocks the spinner. Document this in an email to the rep and the company. In the email say you are doing this for confirmation of what has been agreed, the basis on which you are taking the spinner.
In another example a rep may make sales claims for an item, claims that resulted in you taking on the item. Document this.
This simple single communication step could avoid difficulties in the future if a term or condition that was a factor in your taking on a product is not met.