Incorrectly billed monthly and no response!

I have been receiving statements every month from MBD Attorneys claiming I owe Virgin Active money. My contract with Virgin Active began July 2012 and ended July 2014, all of which was paid in full as stated clearly in the statement received. Out of the 24 installments owed, there are 0 outstanding. MBD claims I not only am still being charged for the contract but that the price has now been increased from R299 to R345? This is absolutely ridiculous! Despite my numerous calls and emails requesting this be sorted out ASAP, there has been no contact made to me whatsoever other than these ludicrous claims landing in my mail box every dam month! No one has bothered to contact me. The only communication they send are the statements claiming my account is in arrears despite the statements clearly showing I have 0 installments left and I paid in full! I have been trying to contact them for months but still nothing!