Clive wrote:
This sounds like the answer, can you tell me how I go about it? The
last time I got in touch with Oyster I was asked for my postcode and
memorable phrase, however I could give them my postcode but didn't know
about the phrase and because of this they refused point blank to talk to
me any further. (This was online.)

My partner was in a similar situation. However, a phone call to Oyster
customer services resolved the situation.