Blacklisting

Hello...! I was renting with Varsity Rental, flat villa de bell situated in Northwest Dessirent ,I was transferred to Pretoria with work related, I put in a notice that I will be moving out of the flat due to work relocation, on these date 29 April 2014 ,It was rejected and I was told that even if i leave the flat i will still be liable for the flat payment or i must pay 6 months in advance because I am moving out before time, I was forced to pay rent regardless of staying or not staying... ,I denied reason being i cannot be able to pay accommodation in Potchefstroom while there is a tenant renting in and whiles I am staying in Pretoria . They decided to blacklist me, there is a default on my name for not paying flat that I didn't use ,I payed all rental amount as I was renting. I returned the keys on 26 April just before I leave potchefstroom. As you know that when a tenants move into the flat there is a deposit amount to be payed, which a tenants suppose to get it back when he/she move out of the flat, but I did not get it back aswell .In these regards I think it is not fair because I am blacklisted for something I didn't use so I am just confused.why am i blacklisted ?