Overcharge on my account

I had a woolworths store card a few years back. i paid the monthly amounts and when i lost my job i contacted them and told them as well. but i still paid as much as i could. i only has a limit on the card of R3000. Bear in mind installments were made towards the card which should have brought the amount owing down. now i am getting calls from attorneys stating my account has been handed over and i am owing over R6000 to woolworths!!! i kept asking them for a complete statement showing me where the extra R3000 came from. they kept saying Woolworths is not providing them with the full statement. how can that be? they charging me an extra R3000 but will not show all my payments from inception!! and to top it all they keep charging me over R20 for each phone call they make to me and i keep telling them to stop calling me until i get the proper statement. Yet they still kept calling me with no proper statement and again charge me for every call!!! this is outrageous. why cant Woolworths provide a full statement yet asking for more money than i had credit for???