Always out of stock

Everytime for the last few months, I have been purchasing visible items online and immediately I pay for it and then a few days later it says my order is on hold and when I call to find out why, the item is now out of stoc**** EVERYTIME! RIDICULOUS! And on top of that, they only provide you with a voucher which is NOT REDEEMABLE for cash and you are now forced to take something from the store to get the cash back, even if you don't want anything or don't see anything nice. WHY must I be forced to take something else and not get my cash back cos your system sucks and the items are suddenly out of stock??!!! And since this happens everytime, the cash adds up and constantly being forced not to cash!!! You guys need to really issue CASH vouchers as I am so sick and tired of this!