Service crash after being a client for over 20 years

And so it came to pass that in the early 90's I app**** for and was given a credit card, and all was well. Fast forward to last week when I checked my statement and found a charge for a cash transaction on on it. So I called the Call Center and was advised that the charge dated back to a cash withdrawal I'd made in Dec 2016 and some other since then. I was told that a 'cash loan account' had been opened and that I owed an amount in addition to the actual balance on my account. I studied my statements and could find no reference to this 'cash loan account'. I was told they'd reconcile the account then come back to me. I was sent a ref # via sms. Then on Friday I was told - Good day Trust you are well. Card reconciliation not done hence we could only do it only for the last six months not from the card was open may you advise as to which months should we do the reconciliation. At this point in time, I am quite happy to close my account - you now need to tell me why I should stay with you after you've been lying/robbing me for nearly 2 years.