Account sent to collectors without notice

I have had membership for many years. I went through some difficulties and fell behind on my subs. Without even a phone call from Virgin active I am now receiving rude and threatening phone calls from a Martin Bishop and Associates. I do not know these people, they ask me for personal information on the phone. And they become very aggressive when I voice my concern. I am a long term customer of Virgin Active, if they have a problem with my account they should call or email me directly before handing the matter to a debt collector. In the very least they should notify me that they are handing me over to a debt collector. I am horrified by this treatment.