Hi Chui,
We unfortunately do not offer support for customizations here, but hopefully we can at least help you figure out what’s going wrong here and point you in the right direction for how to fix things.
The first thing to note is that default-template.php is not an Events Calendar template file. If this is file within your theme, then your best course of action here is to contact your theme developer for insight on how to make this customization.
Next, if you’re curious about how the Events Calendar templating system works itself, which might be helpful here, I’d recommend reading through our “Themer’s Guide” here → https://theeventscalendar.com/knowledgebase/themers-guide/
That should at least help clarify the difference between template files included within The Events Calendar, and template files that are outside of it and in your theme itself.
Let us know if this information helps, and any further questions you might have related to it 🙂
Thank you!
George