What speed are you getting at the router? or at the wall, plugged directly into the socket from a PC with ethernet? Also have you tried a different cable? I'm not saying you're wrong, I'm just trying to help diagnose the problem you're having... and it still doesn't forgive their CS from shoddy work if they haven't already asked you to do the above.
I switched to them from BT on Infinity 2. Their Wi-fi router is terrible compared with the BT one. The speed is dire - often only 10Mbps on Ethernet instead of the 70 I was getting with BT. Their support has been rubbish - “it should be working”. They don’t chase up when I email. They used to have a very good reputation for customer support. I am trying to get out of my contract without much success so far. AVOID in my experience.
So hard choosing a decent provider when you start to look at the reviews. I'm currently with Timico and they are great but I'd like to get Fibre and they charge £54 for maximum speed fibre, inc line rental with a minimum 24 month contract. As I work from home I need the internet without any interruptions.
Great free router and a really helpful company to work with when you compare them to the likes of sky and BT... I would recommend them