Suddenly, no calls. Same on two networks

Hi,
My phone has been reliable for a couple of years but has just refused to connect calls this afternoon. I found this topic, but it refers to options in settings that I don’t have on /e/OS v2.1. I’m really stuck. Under Network and Internet > Calls and SMS it says giffgaff (Temporarily unavailable). Calls and SMS are both greyed out. I am at a loss.

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