Do most AC companies charge service call fees if under labor warranty?

I have a crappy Lennox mini split that has a coil leak. AC company has been out on two occasions to shoot dye in there and finally determined that the entire head needs to be replaced. Found out my wife has paid them $450 so far for this work but I’m still under the original labor and parts warranty. They say they charge the service call fee and for dye and Freon. Seems like a rather worthless warranty to me and I can’t find any details in their paperwork, just that it says 3 year labor warranty