如何说服客人改LC为TT

跟一个客人第一次合作。刚始是同意用lc付款方式。但是因为客人是中间商。信用证是信用证。现在货快出去了。我们想让客人改付款方式为tt。但是客人直接回绝说不可以。不知道该怎么说服客人了 有经验的人帮下该怎么回复了，谢谢了。 since the begining about the payment conditions,? ?at begining you accepted??100%??,??but after that i talked with your boss and agreed to send deposit u$s 25.000 and balance lc. we can not change the payment conditions now.??you he to negotiate balance??with the lc??we he no way to pay tt for the balance