Many cars have a child safety lock on the rear doors - when set it permits the door to be opened from the outside but not from inside the passenger compartment - this is to prevent children from tumbling into the carriageway.
This might be your problem...
Interior door panels usually come off after removing the handles and winders - several screws at the very bottom of the panel that you normally can't see - and then a firm upward shove. But go after the child lock thing first.
Peccavi, August 2013
