u-blox services use monthly plans to handle charges. Plans can either be "Thing Level", one instance of a plan per Thing registered in the platform, or "Pooled", one instance of a plan to which multiple Things can enroll.
Each plan has it's own period which starts at midnight on the day the Thing is activated or, in the case of pooled plans, the day the plan is purchased and runs for a month. Plans automatically renew each month unless deactivated.
Invoices are produced on 1st of the month and charges are calculated based on any active plans which renewed or expired in previous month e.g. a plan that started on the 15th March has a plan period of 15th March to 14th April and would therefore be included in charges for the 1st May invoice. If that same plan was deactivated on 25th April, the 1st May invoice would include two charges. One for the plan period of 15th March to 14th April, and another for the period 15th April to 25th April.
Plans that are deactivated in the middle of their period are charged in full, and charges apply whether or not actual service usage occurs. The invoice will show one line item for each different plan that has attracted charges.
You can check the selected plan and renewal date for your Things in the Thingstream portal, by selecting the Thing in the Thing List.
You can also run a Thing Details Report to check on multiple Things, or check which Things incurred charges on which plans for a given invoice by running a Billing Report.
If you have any questions about your invoice, just send an email to the accounts team who will be happy to help.