What service should I use for one way phone calling?

Question

This is non-programming question, sorry for that. I want to add a feature to my site. This is what I need; Experts will be able to call the customers via fixed number.

Experts will dial 674-432-3434(example phone number) phone number, and then enter customer phone number. Then customer phone will receive a call from 674-432-3434 phone number.

With this feature I want to hide experts' phone number. However I want to use this same phone number all the time, so customer will know that expert is calling.

When customer called this number , not able to talk anyone. It is only one way call service.

I want to have this feature for my website, but don't know what to search for, if any one of you using similar service or know this service please hare with me. I prefer the free one since this is volunteer base half baked startup idea.

Answer 1

After some research I found Twilio has this feature https://www.twilio.com/proxy, but it is going to cost 0.10 cents per minute, so I though making caller phone number private by adding *67 in front of the dial number will take me till some point.