set your twilio things from settings

app/settings/queries/get-available-phone-numbers.ts

@@ -0,0 +1,21 @@
+import { NotFoundError, resolver } from "blitz";
+
+import db from "db";
+import twilio from "twilio";
+
+export default resolver.pipe(resolver.authorize(), async (_ = null, { session }) => {
+	if (!session.orgId) {
+		throw new NotFoundError();
+	}
+
+	const organization = await db.organization.findFirst({ where: { id: session.orgId } });
+	if (!organization || !organization.twilioAccountSid || !organization.twilioAuthToken) {
+		throw new NotFoundError();
+	}
+
+	const incomingPhoneNumbers = await twilio(
+		organization.twilioAccountSid,
+		organization.twilioAuthToken,
+	).incomingPhoneNumbers.list();
+	return incomingPhoneNumbers.map(({ phoneNumber, sid }) => ({ phoneNumber, sid }));
+});