Your post was blank @FionaM4951 so it's not really clear if you had a specific question or issue.
To use your phone on 48 while roaming in the USA you need an active membership plan and cash credit on your account to pay for the relevant services listed here:
Note that making and receiving calls in the USA isn't possible according to that page.
If you have a specific question then please post back with it.
If you need to contact 48 support about this then see the links in my signature below.
