Trying to make +44 uk call whilst in the uk but message saying not part of my data plan

I’ve tried to call a +44 uk number whilst in the UK and it won’t connect. I get a follow up txt from smarty saying that my data plan does not support international calls.  How do I resolve this and get my data plan to recognise +44 numbers as not international numbers whilst I’m in the uk? I don’t want to have to update all my contacts to take off the +44!