Hello Joy,
Please find attached quotation you provided to us before starting this biz,and we just offer to customer based on that,now there is so big difference between you offer and billing,i just talked with customer about this issue and they definitely expressed to me they can not accept additional charge which has not been listed on offer sheet in advance,if we insist on our opinion they will stop all biz with us.
Please understand our position now,we can not accept any additional charge betray to your off