If you have a talk booster, when you call or get called, it will start using those minutes. Whatever you don’t use, will remain until the next time you need extra minutes.

I thought the logic was to begin to use Booster Add-Ons also, but my phone gets locked until I ‘top-up’ ? 

I have plenty of ‘Add-On’ minutes 

Are you saying that your plan is suspended right now? In that case you will have to top up to renew your base plan in order to be able to use your boosters.

But if your base plan is active, and if you have plenty of add-on minutes. you’re good to go. What is your base plan renewal date?