"To me and every customer out there that means - NO EXTRA COST"

To me, "Available Upon Request" could imply an extra cost. Just because it does not mean that to you does it mean everybody else feels the same way. I think you should have been quoted an accurate price, and that is where my agreement ends. I do not think the sign needs to be fixed in any way, as nuts are typically an extra cost at many ice cream places. Just because McDonald's does it one way does it mean everybody else does it that way as well.