Wow, thank you all for so much additional information. And this isn’t even my question! @nick2008, I hope you are getting what you wanted out of this.
@omph, not sure I understand. Do you mean having $50k in charges (debits to your account) or an unused $50k line of credit?
@bythebay, I don’t (think I) need to raise my credit score, which should be impeccable. Do you mean that just by letting this unwanted card sit there, I am hurting my record? (That would certainly be the apparent effect if I just cut it up.)
@basp, your advice sounds very comprehensive and knowledgeable. I will follow it (unless someone else steps in and says it’s wrong!). Thank you.