Once you sign the agreement you are bound by its terms. The manager (or Landlord) could allow you to back-out or modify, but certainly is not required to. Of course, as always, there is the possibility that an exception exists. In other words, if the contract is somehow invalid, void, or even voidable, you can get out of the agreement all-together. To determine this, you may have the contract reviewed by an experienced contract attorney. Also, the manager is likely within his/her own rights by attempting to fill the other apartments before finding a replacement for yours. The reason being, technically speaking, yours is already filled by paying residents, that being you. Management may see this as "good business" but they certainly are not required to fill the other spots first, although if they pursue you for breach of contract their failure to attempt to locate adequate replacement tenants will be relevant. You should contact a local attorney who can read over the contract and discuss it with you.
You are in a pickle-once you signed an 8 month lease, the LL is not obligated to do anything other than honor the lease agreement. Doesn't matter what they said before or after the signing. Breaking the lease early could result in your being sued by the LL for breach of contract. Recommend you talk to a LL-tenant attorney and discuss if you have any other issues that might give you some wiggle room. Best of luck to you.
NOT LEGAL ADVICE. FOR EDUCATION AND INFORMATION ONLY. Mr. Rafter is licensed to practice before the state and federal courts in Virginia. There is no implied or actual attorney-client relationship arising from this education exchange. You should speak with an attorney licensed in your state, to whom you have provided all the facts before you take steps that may impact your legal rights. Mr. Rafter is under no obligation to answer subsequent emails or phone calls related to this matter.