The circumstances would be different depending on whether or not the merchant has completed the transaction and collected the funds.
-If the merchant has collected the funds we have to follow a disputes process which will mean contacting the merchant as a first step (if the payment was knowingly authorised) to request a refund.
-If the amount is pending due to a break in the connection (which prevents the merchant from completing the payment) we normally advise that the payment will automatically reverse after 7 days. We understand however that in some circumstances this is an inconvenience when larger amounts are at stake. We are always happy to remove these allocations if a declined/voided receipt can be sent through or the merchant provides the authorisation code/ written acceptance that they will not collect the funds.
We are working on making some wider information available to explain how reversals work. But in the long term we would defiantly need to address a solution to this issue as it is a tough one to explain given that most users are used to legacy banking processes.