I recently ended my lease on 01/31. My landlord had charged us a lawyer fee for adding someone to the lease. He was giving us random amounts and when I asked for receipts, paperwork, and proof of transaction, he failed to give me any of those. On the day of 01/31, he proceed to charge us ( a different amount that was originally stated) and handed me a receipt that was dated 01/31. He deducted it from my security deposit without giving me a chance to review it. I feel like I am being taken advantage of.
Review the terms of the lease, and determine (a) what deductions can be made from the security deposit, and (b) what charges can be made for lease changes or tenant changes. If the amount and type of deduction for "lawyer fee" is included in either of those areas, then it sounds like the landlord did what the lease allowed. But if not, then the deduction could be improper. If you're in the U.S., you could see a lawyer specializing in landlord-tenant law; or there might be a "tenants' union" in your area, which is usually a nonprofit organization that provides information for tenants to exercise their rights.
He deducted it from my security deposit without giving me a chance to review it. I feel like I am being taken advantage of.
Indeed you are, unless this issue in particular is explicitly provided in the terms of the lease. The reason why I use italics for "explicitly" is that the act of adding someone to a lease is not complex enough to warrant assistance by some lawyer. A landlord is not entitled to unreasonable expenses, especially if he failed to notify you beforehand so that you can make an informed decision on how to proceed.
It is unclear whether you question the legitimacy of the receipt, but you are entitled to proof of the alleged expenses. It seems that you have a viable claim under multiple legal theories such as breach of contract and conversion.
You did not specify your jurisdiction and the amount in dispute. In some countries the tenant might be required to undergo an "alternative dispute resolution" (ADR) venue instead of court. The amount in dispute is also relevant for determining whether the matter would have to be litigated in Small Claims Court or the non-US equivalent. If the lease provides for ADR, then that takes priority regarding how to proceed.
Be sure that your subsequent interaction with the landlord be in writing, since that might make it easier for you to prove your claims.