Mobile number not connecting to network / allowing phone calls

I purchased a Smarty Sim Card from a shop last month, it worked fine to begin with and when in an 16 Plus phone which is kept updated but does not show all applications within the Support app (I've gone forward with this info through the blue support app) and the phone kept my Smarty number withheld when I tried to call the nation long building society earlier today. Therefore I tried to call from a non-application/internet phone and that phone won't allow the Smarty Simcard to connect to the building society (used across the nation) scam/fraud line I need to speak with to report an ID verification email disappearing from my encrypted email account.... Anyone able to advise on how to get through to said companies and get the Smarty number working on every device? Living back home nearby Saint Annes On The Sea, Lancashire. Many thanks.