I dont recall ever seeing or getting a static spark on a cordless phone. And dont know what else you have that might generate static... perhaps low humidity & with some shoes and carpets, the combination will create a static shuffle and shock you elsewhere too ?

Where the phone line enters the house there is usually a grounding conductor tied to the same grounds the electrical panel use. Typically looped to a metal water pipe and usually a ground rod.

You might look around and see if one of those grounds has come loose or been weed wackered.