Deregistration of iPhone from Lloyds Mobile Banking App

Lloyds mobile banking app keeps having "technical problems" and logs out. Lloyds "Help" suggested reinstalling the app. I have had to do this on several occasions on my iPhone and am now informed that I have too many devices registered to this app and to deregister the. In fact I only have one device, my iPhohne, registered. Lloyds Bank are most unhelpful in that when you ring for help they cut you off!

Can any one advise me how I deregister my iPhone from the Lloyds mobile banking app? Thanks.