Collection Agency? CAB Asset management?

CAB asset management called me today and they were very threatening with their call saying they were not a collection agency asking me for money and telling me they're "client" was ready to sue me and saying if i did not pay they're company could look into my assets and collect their money. Who are these people? Are they just a collection agency who was hoping for a sucker who would willingly just give them the money because they tried to call with threats? Is CAB a collection agency? This is all over $1100 amount with Bally total Fitness....What should I do in this situation?