Thinking about this a smidge, you probably can just use voip.ms to (a) order a DID (aka a phone number), (b) setup an IVR for the message, and (c) instruct them to dial an [internal to your account] extension that forwards to your real number, all on the voip.ms platform.
You wouldn't have to set anything up, just pay them for per-minute charge. You will have to pay 2x per minute, once for the inbound, and then outbound to your real number, ..... unless you go through the extra steps of setting up SIP phones.
FWIW; I've used voip.ms for a long time, and just a very happy customer. The biggest trouble they've had was availability issues a month or so ago when they were the victim of a DDoS :-/. You probably could pull off this trick with any of the pay as you go SIP trunking providers ...