In case it’s helpful for anyone, I’ve just spoken with the Phone Co-op, after having some trouble getting online with mobile data. I could access the internet fine when connected to wifi, but on mobile data nothing would load, and I’d see a small cross next to the signal bars at the top of the screen. I did some basic troubleshooting (checking the card wasn’t dirty/dusty, resetting my APN settings, switching flight mode on/off, restarting my phone) but without any luck.
Apparently there was an issue at the Phone Co-op yesterday (Weds 15th) afternoon which was the cause. Their customer support team were super helpful and it only took a minute for them to update my record and fix it. If you’ve had trouble accessing the internet on mobile data since yesterday, it’s worth giving them a ring on 500.