how can i fix a fault on my central locking for golf mk4?

I recently had the bumper replaced after a rear end accident. The central locking was working fine when the car went in, but when i got it back i noticed that the key only opens the front door and not the others including boot. all doors lock fine using the key. The key in the drivers side opens all the doors but this triggers the alarm when you then open the doors. Please can anyone help because the repairers aren't interested?

Thanks

Vicky