ITC listing for paying my rent in advance

my rent is due every month on the 1st. I usualy pay it beforehand because I get paid on the 15th. This people's accounting systems are not up to date. They've now listed my account as default on the ITC and I was never late with my rent. Several times I forwarded the proof of payments of my rent to them but guess what? they still insist that I didn't pay my rent? the bad thing is that they based I JHB and the property is in CTN.