CLAIMING EXCESS A YEAR LATER/ PANEL RITE P/B

my car was sent into PANEL-RITE Panel beaters for repairs after an accident in JAN 2015, after the repairs were completed i collected my vehicle. On collection i was given a clearence certificate from Panel-Rite and was told that NO Excess is owed and that i can take my car home. In October 2015 Panel rite claims that i owe the R1000 going against what was written in that letter , they claim that there was an error on Innovation Groups side and that i owe them R1000 excess. The panel beater persists threatening a summons to court if i dont pay them the excess, surely an eroor was made on there side or Innovation Group.