is it possible to port my number to another sim but keep my contract?

my mum has an iD mobile 2 year contract that ends in october 2025. she wants to switch to another provider and keep her old phone number, but she wants me to use her contract with the iD sim. i just want to know what happens if i port her number to a different provider - will the iD sim stop working? or is there any way to put a new number in it so i can use it? i don’t mind having a random new number, i just want the data plan to keep working, cheers xx