Three months later we still have roaches

Three months and several visits by the exterminator later and we still have roaches! Courtyard Square and the exterminator just can't seem to get a handle on it. The exterminator assured us the bait he was using was effective and the roaches would take it back to their nest and kill the colony. Yet everytime we turn around we have roaches coming under the shared wall with the apartment next door. Should it really take months for them to get the situation under control?