Eco Plus Solutions phone scam - wants to send us "Free" samples, then send huge invoice mercier Quebec

This company phones and tells people that they are willing to send a free sample of toner.  Once we receive the toner, with no invoice, no email address of company on the packing slip.

Try to phone the phone number provided on the packing slip, only to find out it is automated.  Left messages but have yet to receive a call back.

On their packing slilp it has conditions:  All merchandise accepted upon delivery are subject to these conditions.  No product can be returned without prior authorization.  There are no cash refunds.

Phoned to inform them that we were returning their product, still no answer.