chat with a buyer and call back

I want to make some new options.
     First, I want to make an additional function: chat with a buyer. May be anyone did this. I will be very happy to get some help.
     Second, I want to make a button with its help a customer can gets call back. The customer only writes his telephone number. May be anyone have made this yet.

AleksandrModestov wrote:
Hi ,
You want to use c2c platform and buyer chat with seller ? or site moderator ? which one ?

I want to have a chat a buyer with a seller.