@Grace Hartman you gave limited information in your post but I'll attempt to assist you. From what I understand from your post is that you are a landlord in which you have rented your unit to a company so that they can provide corporate housing to their employees (employee).
If this is the case, I am also assuming that the lease in place in the 'company's' own lease since most want to have their own leases. If this is the case then it depends on what the lease says, is there a clause that states they can house their employees regardless of who they are?
Regardless of lease though and moving forward, even so, and lets just assume you are correct and they are in violation of their lease. I'll ask you this: Are you a savvy investor who keeps their eye on the ball? or are you the 'principles' police?
I'm only bringing this up because you mention 1) rent is always paid on time; 2) neighbors have no issues; 3) The tenant's are hardly there (which means less property wear and tear) and 4) I will also assume becuase of the first 3 here, that your property is also being cared for...... seems like picture perfect Tenants....
So... you can certainly be 'RIGHT' and still be a horrible investor making nonsensical arbitraty decisions or you can just be an investor and look at if from that standpoint - sure, you can decide to nickel and dime for additional Tenants and you would be even more justified if you are paying Tenant utilities (if this is the case). It's completely up to you... but keep in mind that just becuase it's on the lease, does not make it right nor does it make any investment sense.... it may be completely situational dependent. In this case, 1) you are receiving rent on time as agreed every month and 2) your property is being cared for... situation dependent... up to you.