Page or Popup in Checkout Process

[imi.mehesz]

The client request was:

 

After checking out, before the payment page, a page or popup needs to presented that "WARNS" a user that a phone plan( phone plan is a virtual product ) is required for full functionality of the watch. 

 

A user can skip the warning, or add a phone plan( phone plan is a virtual product ) from this dialog which updates the totals.

 

The warning must appear, but the user is not forced to add a plan, if they choose not too and can skip to checkout without the phone plan.

 

Anyone can help me with ideas or how can i create this page/popup?

 

Thanks!