Need to fix the issue on the unity project for dynamic loading the texture from server

I have 2 buttons to load the different texture images and when i press the 1st it loads the 4 images in textures and when i press the 2nd button it loads the 3 images in textures. But the problem is when i press the 1st button it loads the 4 images and when i press the 2nd it loads the images but it starting from 5th place. I can't reset the value to 0 when i press the second button. it's not static 4..the textures are fetching from server json url and displaying and it would be vary depend on user upload in the backend.. For example, i have 5 categorys like 1,2,3,4,5 and each category has some images to load in the textures...in the first i'm displaying category list and click any of the category then i'm getting the category_id and loading that category images from json url I want to load the proper images from server based on the category list click