We are using a new ticket provider.
On Zeffy - the buyer can choose the amount for the additional service fee. Zeffy is free to our non-profit and does not charge us any processing fees for your order. 
Zeffy is able to support non-profits like ours through their optional service fee model.  

The default is 15% of the ticket price.  If you would like to have a lower amount or not participate, you will need to change the default to other and then put in the desired amount or leave blank.