AT&T Wireless Hidden Charges on re-upping for 2-year plan, Internet

AT&T cellular has an Upgrade Fee of $18.00 per phone that has been applied to a Family plan that has been in place for 2 years of a 2-year plan and we merely wanted to re-up that plan.  We had 3 iphones and one Razor phone on the plan originally and moving to 4 iphones for a 2nd 2-year plan only to find ALL phones are being charged $18.00 fees for basically continuing with 3 iphones from original plan AND 1 converted to iphone for the next 2-year plan.  I feel this is a ripoff because the SAME service from AT&T for 3 of the iphones will remain intact with only one phone changing to the iphone requirements of service.  We are paying Apple for the upgraded iPhone4's, so why does AT&T think they need to reach deeper into our collective pockets by applying these additional UPgrade fees?