Hotel Hacienda el Salitre

everthing was fine except for fallowing issue i paid the full amount at the time of the reservation like 25 days before when i do the check out they charge 18.00 us dollars because they said, we do not pay the taxes at the time of the reservation.....i do not understand but finally i have to paid.....also i shown to the receptionst the reservation in my cell phone with the proof that i paid my reservation in full but they say,, anyway you have to paid for the tax.....