so ive just launched n8n by local hosting it via ngrok, and it works find but when i try and use my webhook url in vapi it just shows and error when i try and save it but works fine with a make.com webhook can someone help me with this?

ive been working on a ai voice receptionist, ive used vapi and make. how can i make it functional i want to test it but idk what phone number to use could i just my actual phone number and try calling it from a different number to test how does it work? twilio doesnt seem to have the region im looking for