The landscapers worked to quickly to plant new items and did not wait until the old vegetation had time to die. They are irresponsible (in my mind) and should have known better if they had not been too quick to take your money.
Watering the new plants like the bulbs and rosemary only helped the old vegetation to continue growing. You must dig up ALL the old stuff as jvdubb said - every bit of it - it may be necessary to use some type of systemic herbicide and wait (that's the hardest part) to be sure that the old plants are very dead before planting and watering.
Yes, please, upload some detailed photos of the plants and the entire area involved. And please, what is your location generally speaking as it may have some bearing on the answers you receive.
My 'joke' answer would be: Get a goat!
