Lease extension request

I currently have a 6 month lease and would like to extend said lease. My landlord has agreed to another 6 months but wants to draw up a new 6 month lease and charge me another agency fee of 15 % of the annual rent which I had already paid when I signed the first lease for 6 months. Furthermore there is no mention of this in the original signed lease. I would like a letter for my landlord that says I dont think it is fair as a good respectful tenant to be charged an additional agency fee of 15% when I am just extending the lease another 6 months and I paid an agency fee of 15% 6 months ago when i first signed the lease.