If you received the goods you should be liable to pay. Check their invoice and see if there is a 'Romalpa' clause on it. Most commercial invoices have one.
"A Romalpa Clause in a contract provides that until payment is received, title or ownership of goods sold remain with the seller.
In this way, risk of loss and damage pass to the buyer upon delivery, but the title passes to the buyer upon payment in full.
In other words, he must pay in full in order to get title.
WHAT IS A "ROMALPA" CLAUSE?
The use of "reservation of title" clauses (or, as they are commonly referred to, "Romalpa clauses") has become widespread in the sale of goods. Under this type of clause, the seller retains ownership of the goods until full payment has been made, but the buyer is allowed to take delivery of the goods. If the buyer does not pay, the seller can therefore take possession of the goods.
SIMPLE CLAUSES
An example of a simple clause would be:
"Property in the good shall not pass to the buyer until the buyer has discharged indebtedness to the seller for the purchase price of the goods."
This is the simplest type of restraint of trade clause and is basically designed to ensure ownership of the good is retained by the vendor until the purchaser has paid the contract price in full. It protects the vendor in the event the buyer fails to pay for the goods at the agreed time, or is unable to pay the contract price in full due to insolvency."