Game Store Card

I app**** for a Game Store Card a while ago and was given a credit limit of R7,000. Fine. I purchased things with it, but came nowhere close to using my full limit. I am yet to receive a statement of a day old, but that is not my problem. I got the card for the convenience thereof as my wife is pregnant and I wanted to use the card to mostly purchase items such as a baby mattress and power tools needed to put up shelving and such. So today (April 23rd 2020) I went to Game to by a mattress, bath sling and so forth. Come to the till thoroughly believing that I have more than enough credit to purchase said items. My card did not want to take. After three tries the teller saw that my limit was almost full, which is impossible, I have not purchased R7,000 worth of items. So she printed a slip and said slip showed that my limit was basically R3,000. How on earth did my limit go from R7,000 to basically R3,000 without me being notified and given a reason? I was left utterly embarrassed to the point of being mortified. My account is paid monthly, a little more than the amount that I had to enquire after myself instead of getting a statement. Do these people realise that this can negatively affect my credit record which will most likely cause me and my wife being unable to apply for a mortgage for a property that we are interested in? Why was my limit decreased and why was I not contacted regarding said decrease? Do they make a habit of leaving customers with egg on their faces? I may be overreacting, but I am going to close the account as soon as I can and wash my hands of Game and RCS. This is totally unacceptable.