No - The numbers in an advert do not expire because the end date of the advert has passed.
If you are displaying the numbers and they are linked to your Calltracks account, your customers will still have the ability to continue to call you as usual.
The end date in an advert is there to help you to understand when your campaigns are running. It will also help with reporting where you may use identical campaign names, but over different date ranges, and therefore be more easily identifiable in the report results.
When end date is set up in the past, you will not be allowed to visualise the number in listings and it will appear as follows:
As we know, having an advert set up in the past, does not automatically deactivate the number.
If you want us to deallocate numbers from your account, please raise a support ticket from the help button at the top of this screen.