I tried Coinbase for fun a few weeks ago, and once they informed me it would take two weeks to process the transaction I got a bad feeling. I stopped the payment, and used Localbitcoin. It was simple, and got my coins in a few mins. My opinion is that they use customers funds as a way to fund their trading. As BTC is so volatile they can make a few trades with your money, and than send you your BTC.

When I sent in a support ticket to stop the transaction they replied a few days later with a off topic reply. Fast forward a week later they emailed me saying the bank refused to pay them and they can't process the transaction.

You may need to find outside help to deal with this, and keep on trying to contact their support. Also try mailing a certified letter to them. Keep all documents to support that you've contacted them.

Good luck