Small company scenario: What to do when a customer calls about a non-P1 request?

[Robert Werner]

I work for a 15 person software company that will go live with customer support in the next few months.  I've been tasked with setting up their Customer Service infrastructure.  Jira Service Desk will play a big part in this but we do feel we need to provide a phone number in case someone has a P1 request and they don't want to make it through our customer support portal.

In the event that someone calls and it turns out they are making a lower priority request, how do you handle this?  I'm specifically thinking of calls that might come in at 3am.

Any advice would be appreciated.

Robert