Bad customer service

I am really disappointed in Zando's customer service and I do not think I will buy from the store again. I had an issue with an item of clothing that I ordered being out of stock. Fair enough but I emailed and phoned the company countless of times (over 2 weeks) to see if they were getting more stock in the future as I didn't mind waiting but I received no response to any of my messages. They haven't stated that the item is out of stock for over 3 weeks now on the website but anyway. Yes they gave me a voucher of the same value to purchase something else or what I thought but when I try and purchase a product it tells me that the value of my voucher is lower than the value they specified in the email. Technically they are taking money from me. It is not about the value as it is a small amount but the principle because if they do that to everyone it is a problem. I can also say that it is not an amount for delivery as my order fits into the rate qualified for free delivery so why are they taking money off my voucher. I have about 6 case numbers and none have been attended to in 3 weeks.