Dell account blocked from purchases

 I have been buying quite a bit of kit from my Dell account recently. Suddenly I noticed that my orders were been cancelled around 5 minutes after purchasing them with no explanation at all. I used a cash reward for £400 and some reward points to the value of £95 for a new laptop for myself and that has vanished from my account. I contact customer care who gave me my account managers email, which I emailed and got no response, I call customer care who say they will ring back to sort it out and never do. I am so frustrated with this! I like Dell kit but cannot order anything. If it problem with the amount I buy why don't Dell business contact me to arrange a business account. It' seems so stupid that I can't buy from you, we are both losers. Can someone please contact me to sort this out, it's crazy.