I was late once for citi, did not get the late waived. But it did not show on my credit report, that's good.

mm怎么知道在不在“credit report”上？

tell them you did not receive the statement, so they will give you the credit.  But you only can do this once a while, not all the time.

继续打，多试几次嘛，说不定换了一个人就会比较通融，反正对你也没有什么损失

One time late is fine. If you do it two times in a row, it will impact your credit score.