Unfulfilled online purchase supply & Invalid vouch

I made an online purchase at Old Khaki and after a few days only 1 of my items of clothing purchased arrived. The package had no explanation as to why there was just one of the 3 or so items purchased enclosed. I had to make numerous phone calls only to be told that they had messed up my order and did not actually have the stock available which I paid for. I had to wait about a week for my refund to come through and I received an email from Old Khaki with a complimentary voucher to be used online as a gesture of apology for the inconvenience. Since then I haven't been online to make any purchases at the store but have recently logged on and tried using the voucher only to receive an error message that the voucher is invalid. The email with the voucher number has no expiry date so that shouldn't be the case. I tried emailing Old Khaki since 28th December and have received no response. Surely if this retailer wants to have an online store they should have a website that properly manages stock and also have staff that respond to queries related to online purchases. I really am considering never purchasing from Old Khaki again.<br>