Hello, could you please advise — I tried calling a test phone number yesterday. I called from Vapi numbers +1 (380) 208 6442 and +1 (669) 946 1176 to +1 (510) 426 1707(my number), but I received the error: “An error occurred in this call: call.in-progress.error-providerfault-outbound-sip-503-service-unavailable.” There is also another issue: sometimes when I make a call, it appears that the call starts on my side, but in reality the person I’m calling never receives the call. It ends with “Silence Timed Out.” In the messages showing the conversation, it looks like the bot is speaking and the call supposedly lasts about 40 seconds, but the recipient never answers the phone. Why does this happen? Below I am providing the call IDs and describing the issue associated with each one: 7b1e42b5-0692-4d65-9bcb-fe8ed4820afc — error “An error occurred in this call: call.in-progress.error-providerfault-outbound-sip-503-service-unavailable” when calling from +1 (380) 208 6442 to +1 (510) 426 1707 7b1e42b5-0692-4d65-9bcb-fe8ed4820afc — error “An error occurred in this call: call.in-progress.error-providerfault-outbound-sip-503-service-unavailable” when calling from +1 (669) 946 1176 to +1 (510) 426 1707 7b1e42b5-0692-4d65-9bcb-fe8ed4820afc — “Silence Timed Out,” even though the call never reached the recipient and they did not answer, but it shows the call lasted about 40 seconds 7b1e42b5-0692-4d65-9bcb-fe8ed4820afc — “Silence Timed Out,” even though the call never reached the recipient and they did not answer, but it shows the call lasted about 40 seconds https://cdn.discordapp.com/attachments/1471816896864063541/1471817385924235418/image.png?ex=69905041&is=698efec1&hm=91804ba02574a483c6a348f1132aeb339fc8d8c8bc1de8ee53617a3cda416a73&

From the logs, it looks like the calls are timing out or failing before the agent fully connects, which usually points to API auth, webhook response, or number setup issues. I’d start by checking your API key permissions, phoneNumberId status, and whether your outbound webhook is responding fast enough. It’s also worth confirming that your carrier/SIP provider is actually accepting the call and returning audio properly. Are you seeing any detailed error events in VAPI, or is it only showing “terminated” or “silence timeout”? @saio

There are no additional details other than what’s shown in the screenshot. My webhook responds quickly, and I don’t see how it’s related if the call isn’t even going through — or maybe it does go through, but the user appears to be silent. It could possibly be voicemail. I tried calling other U.S. numbers — some calls go through нормально, while others have this issue: either a 503 error or a timeout. I also tried making calls directly from Vapi without using my backend, but the call still doesn’t go through. I don’t understand what the problem is. When a 503 error occurs, my backend receives exactly the same information that I see in the Vapi Call Logs, so I doubt the issue is on my side. However, I don’t understand why this is happening or how to fix it.

Thanks for the details, since this happens even without your backend, it’s almost certainly a carrier routing, voicemail detection, or media handshake issue, not your setup. The mix of 503s and silence timeouts usually means the call is connecting at the network level but failing during early media or audio negotiation. What I’d do is analyze the SIP flow and call progression to pinpoint exactly where it breaks. I’ve resolved this pattern before, and it’s fixable once isolated. If you’d like, we can review it privately and I’ll walk you through the solution step by step. @saio

Yes, I would appreciate the help — but only via chat, since I’m not fluent in English.

VAPI free numbers can only be used within the US and they do not support international calling

I am trying to call US numbers, but the calls are not going through and end either with timeouts or a 503 error. I am not sure that this will start working after purchasing a phone number from you or upgrading to a paid plan. Before I do that, I would like to make sure it will actually work. If I purchase a plan or a paid number now, what guarantees do I have that the error will disappear? When I try to call numbers outside the US region on the free plan, I receive the appropriate error saying that I cannot call non-US numbers. However, in this case the errors are completely different — 503 and timeouts. Please connect me with someone who can provide more detailed logs and clarify what the issue is, because before making a purchase I need to be sure that this works. You are answering the question as if you did not read the context at all. I already specified above which numbers I am calling from and to — none of them are non-US numbers. So why are you giving this response: “VAPI free numbers can only be used within the US and they do not support international calling”?