A landlord will sometimes create an "illusory tenancy," pretending on paper to have a legitimate tenant-of-record in a rent-stabilized apartment. The false tenant then subleases the apartment to an actual tenant at a rent above the legally permitted rate. If you suspect this has happened with your lease, get a "certified rent history print out" from Homes and Community Renewal and take it to a Tenants' attorney. You may be able to sue the illusory tenant and your landlord, and acquire a lease in your name at the legal rent-stabilized rate.
McAdams Law represented a client in these circumstances, and ultimately succeeded in gaining control of the apartment for him. The illusory tenant had to pay over $15,000 in overcharges. The rent was adjusted to the appropriate rent-stabilized rate, which in this case was less than $400.
In these circumstances, landlords collude with accomplices to create sub-tenancies at inflated rents. Using intermediaries, they increase rates and rent apartments to unwitting victims at what seem like legal amounts. Illusory tenancies can be complex and difficult to investigate. You'd be best served by getting a Tenant's lawyer to assist you if you are caught in the net of a landlord's illusory tenancy.