Paying for nothing

Around January i opened an Edgars account because i wanted to get a credit name seeing that i didnt have any debt and the bank needed some references ect.. I opened the account and i received R2500 credit i bought a pair of shoes to start the account and paid it within 3 months. I had credit again because i didnt want to much debt i didnt want it in the first place but i had to have as i explained. So every month since then i had a statement for around R200 i paid every month sometimes more than i should. Today i went to pay my account again and asked them what my available balance and outstanding amout was. All of a sudden i had a credit limit of R1200 and only had R300 available i asked them why when she drew my statements she said there were 4-5 months that i havent paid which is IMPOSSIBLE i told her i draw money and pay it cash every month. I was told by a friend that he once paid cash and received a slip but it was not on the account so clearly im paying the person cash at Edgars and then it doesnt reflect on my account. I have received a sms ONCE saying i havent made payment but i just paid late. I'm not happy at all with this paying my account and not being reflected