Protecting phone numbers on the site, how to implement?

Question

Telephony

There is a notice board. We want to replace the real numbers of each ad with virtual ones.
About 500-900 people per day. Old ads are removed, new ones are added. Only about 400-500.
How best to implement so that real numbers are not shown, but you can contact the author of the ad directly and find out the real number during the conversation.
There was an option to take a pool of numbers (100 pieces) and assign to each ad a virtual number for an hour or two from this list. If you choose this option, then through whom can you sell it so that the price matches the quality?
I thought about a more sophisticated option with an autoresponder robot that focuses on the ad ID.
Maybe you have some ideas how not to give a real number at the first stage?

Answer 1

The "Get number" button, by clicking send SMS with the number from the ad to the number specified by the user.
Limit the number of requests per unit of time.

Answer 2

shut up like crazy