credit card limit

I have a silver credit card with woolworths, but , I am always receiving sm's that my credit card limit has been exceeded , then yesterday I called to and asked the consultant what limit am I exceeding she told me that if I misuse or abuse the credit then that's what happens, so then I asked her that for example, say I am given credit of R5000 then I decide to use it all until I pay the monthly instalment why should that be a problem to woolworths as the money is now mine and I believe I can spend it how ever way, why are they saying I am abusing the card, if this continues can woolworths then deduct monthly all the money I am owing to them until it's paid up so I can close their account because I wont be told how to use my money that I have to repay each month, it's not like they are doing me a favour and I am not paying anything back, this is actually annoying, and speaking to that annoying Xhosa speaking lady was a cherry on top as her reasoning capacity was very poor, this is actually annoying, the next time this happens again I am going straight to ombudsman. I prefer that if there's no credit in my account it stays that way, coz I don't recall asking for limit increase, Pleas