You can change your name on your account via your My48 account:
But it only takes first and last name - there isn't an option for a middle name.
In any case it doesn't really make any difference as your account is identified by your phone number and email address/password and the name on the account simply appears on invoices:
And, as far as I know, these invoices are no use for stuff like proof of identify/address with third parties (e.g. banks) as they don't include the postal/home address.
If you need to contact 48 support about this then see the links in my signature below.
