Your credit profile and score are rocking, particularly given your age. If the Barclays/Apple card isn't costing you anything to carry it (and this is purely an opinion), I'd pay the balance and keep the account open. The damage is done as far as the hit from the inquiry and new account. Personally, I'd let the account age along with whatever cards you actually enjoy using. In a couple of years when you have additional cards to shore up your profile, closing the account won't be such an issue. Just my 2 cents. Congrats on the progress you've already made. Good stuff.
*edit* Also, for whatever reason, I've never had an issue dealing with reps from any card issuer but I've only had my Barclaycard a few weeks.
I'd keep the account open, too. Just my personal preference. If you did close it, the account will still age because a closed account will remain on your credit profile for 10 years, so the biggest immediate impact would be your utilization going up from reduced available credit. Keeping your account open will help your credit marginally, but many don't find the hassle of monitoring another account to be worth the admittedly small benefit.
Plus, one customer rage closing a card will never be felt by a big company like Barclays, and if you don't use it they won't make any money off of you either way. If you keep the account but just never give them any more business, they're still exposed from the $2,000 credit line extended to you. Nothing you can do will be "felt," but if you're just peeved and want revenge keeping the credit line open would be my tactic