1. A transaction gateway in a first network, the transaction gateway comprising a processor and memory and being arranged to: receive, from a user device within the first network via a support application proxy within the first network, a support request from a user of the user device, the transaction including the support request; identify a user identifier of the user in the transaction; modify the received transaction by replacing the user identifier with replacement data different to the identified user identifier; send the modified transaction over a third network to a support application in a second network; receive, over the third network from the support application, a support response in reply to the support request within a reply transaction including the replacement data; identify the replacement data in the reply transaction; modify the received reply transaction by replacing the identified replacement data with the user identifier; send the modified reply transaction to the user device within the first network via the support application proxy within the first network, wherein the support request and the support response are part of a support session between the user and support personnel of the support application, the replacement data lacking personally identifying data of the user.