Ask a landlord-tenant lawyer and get answers ASAP
then the rent can not be increased unless pursuant to the lease terms. Your lease is signed by both parties so it is an enforceable contract. The only way the lease can be increased is pursuant to the terms of the lease itself. There has to be some language inside regarding how the rent can be increased. It probably also gives you the right to terminate the lease if they tried to increase the rent which is your ultimate goal. The fact that they had outside paperwork which showed a different rental amount is not relevant. All that matters is what is stated in the lease itself.