Hi Stanl,
Thanks for your post and apologies to hear you're having this issue.
As mentioned by BumbleVMTech, you would need to remove the 0 and put +44 instead. This should allow the number to be dialled then.
If it doesn't please let us know how long you've been having the issue for. Have you been able to make any calls since landline in Spain? Are you able to text or use data?
Pop back and keep us posted.
Thanks,