First you must find out the clause of the quality problems and furnish sufficient evidence.
首先你的查查有关质量问题的条款,并提供足够的证据。
The buyer has the right to cancel the contract unilaterally if the seller fails to ship the goods within the L/C validity.
如果卖方不能在信用证有效期内交货的话,买方有权单方面取消合同。