Ticketmaster Theatre - getting tickets exchanged


A few months ago I purchased tickets for Derren Brown Showman at the Apollo Theatre via Ticketmaster Theatre.
Unfortunately we can no longer make the date we booked so would like to either exchange the tickets for another date or get a refund
Ticketmaster Theatre turns out is different to regular Ticketmaster so you can't resell tickets via their app.
Ticketmaster are saying there is nothing they can do and ‘Each venue has its own restrictions regarding cancellations and refunds’ so I have to contact the venue
The venue are saying ‘As you booked through Ticketmaster, you need to go back to them to amend your booking.’
So its the classic each side referring you back to other
Any advice as the best way to either get the date moved or get a refund?
Thanks in advance for any suggestions
Replies
If the former I've sucessfully used Twickets for reselling - you sell for price + admin fee paid and buyer pays that plus a transaction fee
Best/safest way I've found but only works if you have the tickets (or a guarantee that they will arrive with you by a certain date)