Rat Infestation in multifamily unit in McKinley Park, Chicago

[Luke Petro]

Hello!

I recently bought a multifamily in Chicago.  During the inspection we noticed some mouse traps and a few mouse droppings--no big deal.  Recently, the tenants started complaining of loud noises in the walls and air ducts, stuff being knocked off counters, and chew marks throughout the kitchen.  I sent a pest control company out and they put down some glue traps and they are supposed to be going to the property weekly for a month.  Yesterday,  I got another call from a tenant who saw a  large rat walking right over a glue trap without sticking and they're still hearing them in the walls.  Im getting impatient with the company I used because they're aren't returning my calls. What is the best way to remove the infestation, or what is the best way to screen a pest control company?