Tisco Metal Manufacturing Co Ltd review: Scamming the foreign supplier

We are writing to seek assistance in resolving an urgent matter involving a breach of agreement by a Chinese supplier, Tisco Metal Manufacturing Co., Ltd.
Our company entered into an agreement with Tisco Metal Manufacturing Co., Ltd. for the supply of metal goods, with a total contract value of USD 21,462.65. As per the agreed terms, we initially paid a 30% advance. Upon receiving the supplier’s packing list and confirmation that the goods were ready, we proceeded to pay the remaining 70% balance.
Attached are the relevant payment receipts and supporting documents for your reference.
However, after receiving the full payment, the supplier unexpectedly demanded additional funds—beyond the terms stated in the original agreement. Despite our efforts to clarify and resolve the matter, the supplier has neither delivered the goods nor issued any refund.
We consider this a clear breach of contract and possibly a case of fraudulent behavior.