Insufficient funds

I have a credit limit of R2500 and owe R275. I've transferred R3000 onto that card today and thought I could use about R1000 in credit whilst waiting for that funds to clear. That would still be way below the R2500 credit limit. But when I tried to make a payment I was told I have insufficient funds. What's the point of the over R2000 credit limit if I cannot use it? Worst credit card ever