指定货代乱费，我想向客户投诉一下，用英语怎么说恰当？

Dear customer,

I am writing to express my dissatisfaction with the designated shipping agent you recommended for our recent shipment to Turkey. Despite shipping only 6 small boxes with dimensions of 1.03m x 1.04m x 1.05m, we were charged an unexpected and excessive fee of over RMB 800 for a variety of costs including port operation fees, cfs charges, b/l, and customs fees.

As a loyal customer, we are disappointed with the level of service and the unreasonable charges we have been subjected to. We would like to request an explanation for these costs and ask for a review of this matter. We hope that in the future, we can rely on more transparent and reasonable pricing in order to maintain a good business relationship.

Sincerely,
[Your Name]

P.S. We apologize for any inconvenience this has caused and will take this experience into account in future transactions.