It could be that you were charged for going over your allotted minutes. Usually, outbound minutes, which are not free. Incoming toll-free minutes are not free as well.
You can view your invoices to get a detailed account of your charges.
It could be that you were charged for going over your allotted minutes. Usually, outbound minutes, which are not free. Incoming toll-free minutes are not free as well.
You can view your invoices to get a detailed account of your charges.