It doesn't matter - legally, they have to Unsubscribe you if you request it....
If there is no Unsubscribe option/link - they are not acting in accordance with marketing laws.
If you never signed up to receive emails, that is illegal too.
But, if you signed a petition or other form where you had to click a link there's likely to be something in the T&Cs which says they add you to their mailing list. However, you can still opt out by unsubscribing.
Check the details in this site for more info on how to deal with it if they won't unsubscribe you.:
https://ico.org.uk/for-the-public/online/spam-emailsI'm in fisticuffs with O2 network for the same thing at the moment.... Unsubscribed 4 weeks ago and still receiving emails, plus they sent me a 2nd SIM card after I told them I wasn't going to sign up with them. The only contact they offer is Live Chat, which they want a mobile phone number for! I've told them through twitter messaging (ongoing for the last few days) that if they fail to act on my requests, they will be reported.