Seatme Disappointing Service

Booked tickets for a show at Attebury Theater through seatme, unfortunately we can't attend the show on the day we booked due to unforeseen circumstances. Called the to ask if they can change our booking to a different day however the person I spoke to just point blank refuse to assist by saying their system does not allow for changes to tickets. If I asked for my money back I can understand, however changing from one date to another especially with seats are available should be possible. The person was just not interested in helping.