Please assist

My contract was due for upgrade, so I decided to cancel it on the 14th December. So today 20th December when I want to check to confirm that is canceled, I'm told that I'm having outstanding amount of R1000, because my contract is ending January 2022. The person who assisted me didn't tell me that if I cancel it I will have outstanding amount that I must pay. If I was told that I was going to wait for January. But I was not yold he even gave me the reference number and just say is canceled. Want must I do now.