Lockout of GardTec alarm GT480?

I think our installer has set our system to go to 'lockout'. It went to 'service due' with a chime and the manual implies that he chose to programme this in. Thus it is too coincedental that now it's lon ockout status. He says he needs to come over and take it apart, reconnect from mains etc. Is there nothing i can do to avoid getting him involved? And has anyone heard of such scams elsehwere?