Trying to access certain websites, including innocuous ones like archive.org, is blocked for me despite →

Using Chrome to access such sites sends me to https://www.three.co.uk/support/internet-and-apps/accessing-and-blocking-adult-content.
So, how does one get around this?
Edit: 1) I should note, this is as of this afternoon; I’ve been with iD for three years and this is the first time I’ve had this problem. 2) This is while using 4G, not any other kind of networking like a home Wi-Fi network or whatnot.