a. If you don’t have a phone number, get a cheap 1800 number from Grasshopper.com.
b. You could also get a free Google Voice number, that you can forward to another number or voicemail.
c. Several of the free templates we provide allow you to edit your header graphic. This would be a great place to post the phone number for your store. Here is a kb article on how to edit your header image with a free service called Piknic.