When you log into your account, look for manage my details. With that look for username. Usually your username is your email account. You can change your username (email account to a different email account) there.
If you're able to do that there should be no need to call customer service
Hey there @Trisha2 , hope you had a good bank holiday weekend! There's some good info above from @KingAmo so hoping you managed to get this sorted. Let us know if you have any additional questions though that the community could help with at any point!