How to hide the buyer's number from the seller?

Question

Telephony

I act as an aggregator and I need to transfer the buyer's number to the seller.
How to do it so that:

1. The buyer left his number on the site
   
2. I changed it and gave it to the seller
   
3. Then, when the buyer calls from the seller to the spoofed number, the seller's number is also substituted
   
4. After the transaction between them, on the numbers they received, they were met by an answering machine or something like that
   
5. Also a nice plus would be the ability to record these calls.
   

Are there any ready-made solutions on this topic or how can I implement it as cheaply and simply as possible? Thanks in advance!

Answer 1

Cheap in any way
We put Asterix, take virtual numbers for rent and do

Answer 2

One common number + entering the buyer's code.
You land the common number on Asterisk. The buyer code is checked through the key-value DB (embedded in *).
No one will sell many numbers (at least ABC, at least DEF) cheaply, and they need to cover the number of simultaneous "transactions" during the maximum duration of the transaction.