I've been dealing with a fibre upgrade issue for three months now. Four times in total their support has offered to call me with an update. Twice they scheduled a specific date and time for the call. I've yet to receive a single phone call or email from them.
Their checkout flow can break. In some browsers it'll get stuck in an infinite redirect loop. If you're using edge you'll get redirected to a page that shows the ~10 year old BT Infinity branding, with a totally different style, packages, and prices.
Their chat bot is of the kind that decides whether or not you're allowed to speak to a human based on what it thinks your question is.