Stopped making calls while roaming

[Bucks1]

I came to Lanzarote 5 days ago. I bought the 7 day roaming pass and enabled a spending cap. I could call out the first two days, but since then it says number not valid. That is the same for calls to the UK or to Lanzarote numbers. Data is still working and I can send and receive texts. My husband called me without issue, but I couldn't call him back.

I've tried restarting the phone. The only available network is Orange, Vodafone es wouldn't accept me. There has been no spending on the account, so it's not the spending cap. I have failed to get through to an adviser on the chat, so I need help!

[Bucks1]

I've just put it onto airplane mode and off and it connected to movistar network. Now it just ends the calls rather than saying not valid. 

[bristolian]

You've mentioned that "it's not the spending cap", but how much headroom in the cap do you have? There have been instances of "inclusive" usage still needing to have some wriggle room in the cap, and failing when there's not.