Vodafone Payg plan question.

Hi. I'm not too familiar with payg. My mother is on Vodafone payg. Her current plan gives her Vodafone to Vodafone calls for €20 top up a month. Think it's a pretty old plan. Want to get her onto another Vodafone one that gives her calls to all mobile networks and landlines. Not worried about data, as she uses a simple Doro phone. She also calls the UK occasionally, max once a month or could even be every two to three months. Is there a plan or add on that would cover that or is it best to add extra credit for that?

Thanks.