回复：最近collection company 总打电话过来催一笔

you don't have to do anything with them, simply because they don't have legal right to deal with you. In order to deal with you, they have to be authorized to do so by the original party. Normally, if you ask them for the authorization document, it will kick them away. Later you will find that there are many such so called "collecting company". In fact they are one or two person, probably home-based business. They sell these informations to each other. If one can not get money from you, he/she will sell the information to another such a "company".