You mean how do you buy a plan with the cash credit on your account?
You just buy a plan as normal but at checkout choose the option to pay with your cash credit rather than using your payment card.
That option will only appear if the amount of cash credit on your account is equal to or greater than the cost of your plan.
If you don't see that option at checkout then you'll need to contact 48 support for further assistance.
See the links in my signature below.
