Typically this will more than likely be Pro rata billing.
Pro-rated billing is an invoicing method that charges customers based on the proportion of the service they have utilized in a billing period. In this instance your first bill will consist of you being charged from the first day that you connect and then additionally a month in advance.
In other cases, if you are billed by the network directly, it will also be due to the fact that Ice comms cannot directly apply the our discount to your bills so you are paying the pre discounted rate. You will have have received an email from us at Ice asking you to invoice us for your discount so we can get this paid back to you.