It shouldn't be difficult to cancel a credit card but here's what I've done (so far) to cancel a $500 CL (No AF) card issued by my local CU.
(1) Was told by CS via chat the request can be sent using the Secure Message option in my online banking.
(2) Message sent as instructed.
(3) Response received that I must send an email from my personal mailbox (must match what they have on file) and include the entire card number and my full SS#. 
...for security reasons. I don't think I've sent an entire cc# and a full ss# in an email...ever.
(4) Decided to call customer service to cancel. Rep informs me to write a letter and include a photocopy of my license and credit card. Snail mail? No, thank you.
If you're keeping count, I've attempted to cancel this card 2.5x's
with no luck. I guess I have to go into the local branch now. I know, I know...First World Problems...but ugghhh!
Ok...rant over
@Anonymalous wrote:I'd document that they told you to email your full card and social security numbers. From a security standpoint, that's insane. Email is not a secure medium. I agree. That response basically suggests my email account is more secure than their own online banking secure messaging feature?!
That suggests their CSRs are poorly trained, as do the contradictory demands. They also seem to have a business model centered around making it as hard as possible for customers to leave, which I also consider a huge red flag. Despite the inconvenience, I'd go into a branch or send certified mail to cancel all my accounts, because at this point I'd want to sever all ties. This as well. I work third shift so that's that...
Also, we have a mortgage, another cc, a PLOC, and an auto loan with them so I'm definitely looking at them sideways right now...
@Ceewin wrote:
@Anonymalous wrote:I'd document that they told you to email your full card and social security numbers. From a security standpoint, that's insane. Email is not a secure medium. I agree. That response basically suggests my email account is more secure than their own online banking secure messaging feature?!
That suggests their CSRs are poorly trained, as do the contradictory demands. They also seem to have a business model centered around making it as hard as possible for customers to leave, which I also consider a huge red flag. Despite the inconvenience, I'd go into a branch or send certified mail to cancel all my accounts, because at this point I'd want to sever all ties. This as well. I work third shift so that's that...
Also, we have a mortgage, another cc, a PLOC, and an auto loan with them so I'm definitely looking at them sideways right now...
Yes, that's the whole point of a secure messaging system. It should be built from the ground up to be secure, have end-to-end encryption, and not rely on unknown third parties. Modern email does have some encryption features, but still fails on those three points without proprietary technology on both ends. That's one of the reasons why faxes haven't gone entirely extinct -- it's an even older technology, but it's inherently more secure than email, so it's still used in medicine, technology, and even credit (I had to fax in some supporting documents last year for a CC application.)
It sounds like you have a strong relationship with them, which changes things a bit from my perspective. You might want to try to talk to a branch manager and express your concerns. There's a failure of some kind here, but it could just be a few CSRs. And we all know that CSRs are a very unreliable source of information.