Reactivate my MTN line

Hi, My line has been dormant for about 1yr 3 months now but I have tried to reactivate it and even to add credit but it is yet to work. When I checked my balance using *310# it showed that I have a balance of N540 on it still. Please help me reactivate it or advise me on what I should do. My number is 08068376357. Thanks.