Shipped a 20 CBM, 272‑carton LCL load out of Yantian on 5 February; it cleared Miami late March. My forwarder billed the full 20 percent Section 301 duty, but everything loaded before 1 March should still get the 10 percent rate. I discovered the mismatch after paying and now they claim there is no refund path. Anyone here wrestled a Post‑Summary Correction or protest through Customs and actually recovered the difference? Insights on pushing a reluctant broker or switching to a new one would save me and others from eating avoidable costs.