Taco Bell

I went to the Taco Bell in Fresno and ordered the Doritos Nacho Box which is $5.50 comes with a Crunchy Doritos taco supreme, burrito supreme and a regular crunchy taco and a drink. "From the second I walked in the guy was not very friendly" I asked the cashier "Rodney" to substitute the crunchy tacos for soft tacos. He told me my total is $6.48. So i asked him how much the tax is because the meal is only $5.50 and he said .48 cents is the tax. So i asked him why it is coming to $6.48 because that is charging me almost a $1.00 in tax and he said yes and just looked at me. So i asked him again it the meal is $5.50 and the tax is 48 cents that does not add up to $6.48 so where is the other 50 cent charge coming from and he said I dont know that is what it is telling me the tax is. I told him yet again that I want to know where I am getting charged an additional 50 cents and he very rudely made a very loud sigh and then said we are charging you for substituting the crunchy tacos for soft tacos...REALLY? I have always substituted crunchy for soft tacos and never was charged. I asked him to cancel my order and he said fine and handed my money back. He was very rude, I would like to understand why the extra charge for a soft taco over a crunchy taco, that just doesnt make any sense?