Extremely late delivery with no feedback!!

I ordered a phone online on 19/05/15 and paid extra for express delivery which was suppose to take a day to be delivered. I'm posting this on 28/05/15 and I still don't have my phone. I called and emailed numerous times without proper feedback as to why it is taking so long. I called again today and the consultant only said they are investigating and she would call me back which she didn't. She said it won't be delivered this week so I must wait another weekend without a phone. I bought it on account and my instalment is due but I have no phone. It should take 3-5 working days to be delivered and I'm waiting more than a week which is completely unacceptable. The online service is terrible! After I get my phone and pay the debt I will be closing my account.. The consultant did not even get back to me or reply to my emails. It has really inconvenienced me and I'm very disappointed with the service! Unacceptable from such a big fashion outlet.