IOS telecom Extreme overcharging on call placed on pay phone Internet

On 9/6/13, I stopped at a rest area off I-10 near Wellborn, FL.  I was on the road for the day and had inadvertently left my cell phone at home and needed to let my family know they wouldn't be able to reach me.  The pay phones there would only allow credit card purchases and the only rate listed on the phone was $.50.  I made the call, lasting 3 minutes.  The cost on my card was $26.35.  

When I called the number listed on the charge, I was told the posted amount was only good for coin calls (which were not allowed).  I was also told I had the option to listen to rate charges before I placed the call -- That was not an option.

The company said they could credit $7 back to my account.  They said they don't make any money off the calls, that the charges were for the transaction fees.