It looks like the server is using module: mod-progression-system -> GitHub - azerothcore/mod-progression-system: ChromieCraft Progression System
Individual progression on my repack using this module: GitHub - ZhengPeiRu21/mod-individual-progression: AzerothCore Individual Progression Module
You can stop your level with mod-dynamic-xp which is in the config folder in my repack.
You can change the setting level -> dynamicxp.conf