你们俩个人之间的口头协定已经足以要求他还款，报警不会影响您的学生签证。您的这个情况更倾向于一个民事纠纷而非一个刑事案件尽管这个数字到达一定级别之后就会成为刑事犯罪，您也可以尝试雇佣一位律师为您撰写一封demand letter来索要欠款。也许您的前男友可能只是无力偿还这个债务，有的时候我们在交往过程中只看到了人的好的一面，也需要在日后多加小心。
Your verbal agreement is sufficient to require him to repay you. This is more a civil matter than a criminal matter for the police although it might amount to a crime. Maybe the boyfriend is just simply unable to pay. Sometimes we only see the good in others, and we need to be more careful.
