Sounds like it could be related to your Content Lock setting.
If on Pay Monthly you can find advice on adjusting this to allow access to adult (18+) sites here:
https://ee.co.uk/help/security/staying-safe-online/switching-content-lock-on-or-off
If on Pay As You Go you will need to call EE with a credit card handy to pay a refundable transaction for them to remove it, or visit an EE Retail Store with Photo ID.
