I had a similar situation on FI with seat selection

AS Website: "Seat Selection Included" call FI @ 800-xxx-xxxx to select seats"
Me, calling FI: "Hi I'd like to select seats"
FI Agent: "That will be $140 (two people two legs 35/leg)"
Me: "No, not according to AS' webpage, your agreement with them includes seat selection"
FI Agent: "Sorry that's what we charge"
Me: gives up on FI, calls AS: "FI want to charge me seat selection"
AS Agent: "FI Can charge whatever they want"
Me: "Not according to your [AS] website. Someone at AS negotiated the contract with FI, needs to pull the contract, call FI and remind them of their obligations under the AS/FI agreement"
AS Agent: "We'll get back to you on Monday" (it was Friday)
Monday: "Hi I'm calling from FI, so you can select seats"...

So it can work out.