Thanks for your reply, Rob. 

I know how to change the name of the boundaries and changing the IDs is my question. The reason for that is that when I get summary reports of my DPM to see which walls the particles were trapped on, it shows that based on the wall ID (not based on the wall name, sadly). Attached is a sample screenshot. For that, I have to refer to the boundary conditions list and decipher the wall ID every time. Worst of all, these IDs change in different cases in fluent and it seems that they are randomly generated. Do you have any solution for that?

Those zones that say the particles were trapped are the walls. But you can't say which of the walls 1 to 5 they are based on the IDs (e.g. 7524, 7940, ...)