With Pay & Go you are not really tied to a contract unless you are network locked, in which case they apply £15. From any service providers point of view, Pay & Go is a variable payment unless you use a scheme like Simplicity.
As a Pay Monthly customer is free to do as you are contracted for the period of time.
So from a business point of view it does make sense , for charging for the privelege of moving networks or at least having the potential.
Samsung Galaxy S10, Samsung Galaxy S21 Ultra
