Hi @Mocash21 Seems to be limited network support in UK for Samsung Devices. upon checking limited to iphones or Google pixel/Nokia on all the main networks. Sky Mobile support some Samsung devices but the Z Fold 4 was not listed. https://www.sky.com/help/articles/sky-mobile-device-capability
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .