Double charge pensioners

My mother recently booked a weekend away on the website. Upon checking in they requested her credit card as the amount was on reserve and she needed to pay. They have now double charged her and upon contacting them they acknowledged the double charge but claim they are unsure how to reverse the charges. Considering she is a pensioner, do they belive she has excess funds laying around until they figure out how to correct their mistake? We are utterly dissapointed.