The money is reserved on the customers card for up to 28 days.
However, Anyday orders can only be captured for 7 days.
If you have Anyday Pay, your Visa and MasterCard transactions can be attempted to capture for up to 179 days. However, after 28 days the change of it being a successful capture is a lot lower, as the money is no longer reserved on the customers card.
At any time, if you cancel the transaction, the reserved amount should be released on the customers card.
If you have cancelled the transaction in your backend, and the amount has not been released, the customer should contact their bank.