Bosses don't like receiving snotty letters of complaint and will pass it straight to the department head, this way your complaint gets dealt with from the top down and not the bottom up! Just make sure of all your facts when writing, tell it like it is, don't embellish anything. Make sure you mention your are a Gold Card holder.
You do realise they don't read their own post don't you.
It will be opened and read by their PA, and then passed onto the executive complaints department.
Its the same in all large entities.