Yes they absolutely can sell your debt. They sold my mortgage twice
I went from Soverign Bank to something else I forget, now I am with Bank Of America, they do it all the time.
I would also get on the phone and start seeing what can be done. They don't want to loose what is owed , so I would think they will work something out with you.
Good Luck
The firm collecting the debt has nothing to do with the credit card itself. They are debt collectors they work for everyone not just a specific credit card company.