Seller billing me (buyer) for lock change

[Emily Holbrook]

Hello real estate professionals,

I purchased an investment property from someone who is now attempting to bill me $550 for a lock change after closing (he's the middleman/seller and we needed to let contractors in the property for quotes). Typically, keys are exchanged at closing -- isn't it the seller's responsibility to ensure the buyer can enter the property after closing? Thank you in advance for any advice you may have.