o2 number not recognised

[RoyD8]

I have an o2 SIM in a switch / controller for switching on my heating remotely. Over recent days, when I dial the number, a recorded message tells me that the number isn’t recognised. The system has worked perfectly for almost 10 years. Advice welcome.

[jonsie]

Is it payandgo?

O2 are becoming quite keen on the 6 month top up

Or is it a data only contract sim?

[Enlli]

10 years. May be a 3G PAYG SIM or system where 3G has been turned off.