Can the reminder letter issued by micro-loan be rejected?

However, after being rejected, it will be subject to other forms of collection.

The dunning letter is not a legally binding court notice, so you don't need to sign for it. However, your rejection of the reminder letter shows that you don't really want to pay back the money. In this case, the other party may take other measures to collect money, such as directly taking you to court and asking the court to enforce it.