texture packs/ resource pack will not turn off

when i go into my world setting to take off a texture pack for example the Halloween mash up pack one, so I can use the default textures of Minecraft when i load into the world it will put the texture pack back on even though i took it off in the world settings. I can switch texture packs fine but i can’t take them off of a world that had them on. this has been happening since before the wilderness bound update.