Your business relationship is with the merchant directly and solely, so I am afraid there is nothing we can do to intervene in the case of a single disagreement. We do not have control over the merchant's funds or business and have no way to force them to pay you, nor do we have any contact information for the merchant that hasn't already been provided to you.
If a merchant is not responding or making payments I'd recommend halting any further promotional work you are doing on their behalf, and to avoid a situation like this it would not be a bad idea to strike up a relationship with any merchant you work with in advance by contacting them before or when you join their program so that you can determine who is actively responsive and who is not before you start advertising for them.
