逾期付款的委婉提醒技巧 — 国际贸易填空题

在催款函中，语气应随逾期时间递进而加强。假设一封函件写道：We have written to you twice on this matter, but so far we have ______ received any remittance from you. 语气由此从委婉提醒升级为明确催促。判断该函属于第几阶段催款函？第一阶段的委婉提醒句式应为：We would like to ______ your attention to the fact that your payment has been overdue. 请依次填出两处空缺。