Dont worry!
The theft took place last year so GDPR does not apply
http://www.dailymail.co.uk/news/article-5838189/Dixons-Carphone-reveals-uncovered-unauthorised-access-customers-data.html
https://www.theregister.co.uk/2018/06/13/dixons_carphone_breach/
https://www.bbc.co.uk/news/business-42637820