If the buckle slides of you can re-attach it or call the company. Maybe you put it on to tight aswell because if the buckle is to tight it can snap
This has happened many times before with me and fellow riders. Just contact the company to get new ones and if they keep breaking then I would look at another brand.
If it's the belt buckle, you can call the company and they will give you 2 new buckles for free!